This is, unfortunately, one of the chronic fallacies that make voting security experts tear their remaining hair out. The security models are completely different so what banks do is completely irrelevant to voting.

There are no secrets in banking. Banking transactions are all auditable, a bank has a complete list of where all the money came from and where all the money went. In most cases, the transactions can be reversed if challenged. Even if they can't, the bank can say "you sent $100,000 to the Third State Bank of Bezerkestan, account 5551212, too bad they won't give it back." Plenty of stuff is partially secret, e.g., a bank may not report your transaction details to anyone but you, but it's not completely secret.

The key to voting security is that the contents of your ballot is secret from everyone, including you. There's a list of who voted, there's a list of what the votes are, and there has to be no way to link the two. Computers are really bad at that.