With the serial numbers and massive storage all they’d need is a pathtracking software and to standardize scanning bills to create records at POS.
Sure there’d be gaps but this’d be automatable, so no more FBI agents in a room copying serial numbers to avoid marking the bills. Then whenever voxel scanning happens a bank worker could scan a whole palette of currency and record its data.
So not 100% but significantly more than previously.
For the most part, not really.
These bills were withdrawn from the bank by Person A, and later deposited in a different bank by Person B, who is a flea market vendor (you know this because financial records and other transactions already tie them to the flea market organizers). You can reasonably infer that Person A attended the flea market in the intervening time period and bought something worth that amount from Person B.
It would only start to become difficult to track when multiple person-to-person cash transactions are done in a row – as in the case that Person B spent the cash on drugs from his drug dealer instead of depositing it in his bank account.
At least where I’m from, people who participate in the flee market do an insane amount of person to person transactions, and a good chunk of them don’t use bank accounts.