Yes you can. You're vastly underestimating the size of an f64. Give me a concrete example of a money operation that fails with f64 (for normal companies; assuming you aren't a stock exchange or Visa or whatever).

0.1f64 + 0.2f64 != 0.3f64

Why not?

Encoding in assumptions about a fixed amount of supported currencies in a system is broadly speaking not a good idea