"Fintech" is extremely broad, and most of what gets called "Fintech" is really communication. Communication between firms, between traders, between systems, between ledgers, etc. There is no industry-wide "right" way to program anything, because the right way is ultimately whatever way the other party you're communicating with will understand.

If you're dealing with a party who tracks currency in cents, then tracking currency with more precision than that is going to lead to rounding disagreements. Vice versa if you deal in cents but they deal in tenths of cents. And so on for all the other advice in this document.