You can, but: - it's still advisable to wrap ints in some class to be able to distinguish ints that are already multipied and ints that aren't. It's also better cause then you can overload operators. I've written graphic demu using fixed point numbers (floats) without wrapping them, and it was very painful and error prone. So you still work on objects and not on primitive values.

- there's a problem with how much precision you need. Different countries specify their way to round up doing money calculation differently (even with the same currencies - see Euro). When you use ints you have the assumption about precision repeated all over your codebase, which make it harder to change when tax law changes or you want to support other countries. With BigDecimals most of the code is universal.

You shouldn't use fixed integers. What happens when you need to represent a fraction smaller than what your largest integer can?

For financial calculation you use a dynamic integer type that expand as needed.

64 bit ints in cents/pence/whatever should be OK. 32 bit ints are too small. Even in Zimbabwe which issued $100tn bills 64 bits should be enough.