What you're describing is called fixed point arithmetic, a super cool technique I wish more programmers knew about.
Proper finance related code should use it, but in my experience in that industry it doesn't seem very common unless you're running mainframes.
Funnily enough, I've seen a lot more fixed point arithmetic in software rasterizers than anywhere else. FreeType, GDI, WPF, WARP (D3D11 reference rasterizer) all use it heavily.
Ah yes, well known very complex computer engineering problems such as:
* Parsing JSON objects, summing a single field
* Matrix multiplication
* Parsing and evaluating integer basic arithmetic expressions
And you're telling me all you needed to do to get the best solution in the world to these problems was talk to an LLM?