Your two questions are (along with an inserting of your assertion, too):
1) 'Is this [the overthrew the tables of the moneychangers for Jesus part] symbolic of the end of the Old Covenant and the start of the New Covenant?'
2) 'It marks the end of sacrifices, but does it also mark the end of tithing?'
First of all, the assertion 'It marks the end of sacrifices' is debatable. According the letter to the Hebrews (9:12; 10:1-14), and many other Bible texts, the happening that marked the end of the sacrifices was the offering - for Jesus part - of his perfect body and blood. Before the Messiah sacrificed himself for 'the world' (Joh 3:16) the animal sacrifices performed to the Jerusalem temple were valid (if they were made with right motives, obviously) from God's viewpoint.
Now, returning to your couple of questions, we may say that the answer for both of them is "No".
You say (bold is mine): 'Jesus' actions in clearing the merchants and moneychangers outside the temple physically stopped all trading and exchange. Not only did this put an end to the sacrifice of animals, but it ended the tithing. Neither was possible any longer.' Also, 'When Jesus stopped the exchange of money and sale of animals at the temple He physically made it impossible to continue with the sacrifices and the tithing. He does not say to stop tithing and sacrifices. He physically puts and end to it.'
Now, really, it is 'impossible' that was 'impossible' to perform sacrifices and tithing after the 'overthrowing' action of Jesus, because this was performed by the Messiah twice!
The first time was around the Passover of 30 CE (Joh 2:13-15), instead the second time was around three years after, probably on 10 Nisan 33 CE (Mat 21:12-13; Mar 11:15-17; Luk 19:45-46).
At this regard, consider, please these following comments (bold is mine).
Robertson (Word Pictures in the NT): "John (Joh 2:14) has a similar incident at the beginning of the ministry of Jesus. It is not impossible that he should repeat it at the close after three years with the same abuses in existence again."
Matthew Henry (Commentary on the Whole Bible): "What he [Jesus] did (Mat 21:12); He cast out all them that sold and bought; he had done this once before (Joh 2:14, Joh 2:15), but there was occasion to do it again. Note, Buyers and sellers driven out of the temple, will return and nestle there again, if there be not a continual care and oversight to prevent it, and if the blow be not followed, and often repeated."
The Cambridge Bible
"12–14. The Second Cleansing of the Temple (Mar 11:15-18; Luk 19:45-46).
It is clear from the other Synoptists that the Cleansing of the Temple took place on Nisan 10, not on the day of the entry. St Mark says (Mat 11:11) that 'when he had looked round about on all things there, the eventide being come he went back to Bethany'. In point of time 'the cursing of the fig-tree' should precede the 'Cleansing of the Temple.' St Mark adds to this account 'would not suffer that any man should carry any vessel through the temple'. St Matthew alone mentions the healing of the lame and the blind, and omits the incident of 'the widow’s mite', recorded by the other Synoptists. The first 'Cleansing of the Temple', at the commencement of our Lord’s ministry, is recorded Joh 2:13-17." (the same standing you may find in E. W. Bullinger, inside his Companion Bible, on Mar 11:16; also, Jamieson-Fausset-Brown in their Commentary on Mar 11:15-18)
NET Bible (note on Mat 21:12): "John (2:13-16) records a cleansing of the Temple at the beginning of Jesus ministry." So, this implies that the 'cleansing' reported by Matthew was the second.
Now, it is clear your claims are without a basis, because it wasn't 'impossible' for the money changers and animal sellers return - after some time from the first Jesus' cleansing - to their shady business. Then, Jesus didn't stop sacrifices and tithing at the time of his two cleansing of the Temple. Like I've said before, was the offering of Jesus to ransom for mankind that this happened, really.
If we have to pick a real symbolic event that could represent the 'divide' between the Old Covenant and the New one, this would be the ripping of the curtain that divided the Holy from the Most Holy (Sancta Sanctorum). In fact, did happen that "instantly, the curtain of the door of the temple was torn asunder, from the top to the bottom; and the earth shook; and the rocks rived", et cetera (Mat 21:54, James Murdock).
Hebrews 9:12, 23-25 confirms fully this conclusion, comparing Jesus to a High Priest that enter into the Sancta Sanctorum to offer his own blood before IEUE (יהוה), for the sake of all mankind.
Really, instead to think that the purpose of the two Jesus' Temple cleansings was the stopping of the Temple activities like sacrifices and/or tithes, you have to think about the correct conclusion of Mac's Musings when he said that "Jesus wanted to stop the desecration of the temple courts being used as a market by money changers and traders charging [...]." (bold is mine)
This is confirmed by a particular mentioned only by Mark (11:16): "and would not suffer that any man should carry any vessel through the temple" (Jubilee Bible).
The Cambridge Bible (cited above) commented (bold is mine): "'He [Jesus] would not allow laden porters and others to desecrate the honour due to His Father’s house by crossing the Temple courts as though they were public streets, 'quasi per plateam' [according] Bengel.". This particular is peculiar to St Mark."
What an important lesson for us was given from the Messiah! We have to divide our daily activities, not forgetting that the things belonging to God are superior to the profane things. And that we must not mingle these two areas. An example? Taking advantage of our spiritual 'ascendancy' over a religious community to squeeze money out from 'thirsty and hungry' (spiritually speaking) people...