e.g., 7 * 215 = 1505.
(I assume that this is how "fixed point" algebra works, although what I assume computers do with floats and what they actually do ain't exactly ever been similar.)
You might enjoy reading about IEEE-754, then: https://en.wikipedia.org/wiki/IEEE_754-1985
Assuming that the order of magnitude is fixed, this is of course doable, but according to my experience the order of magnitude does not converge.
The solution is, of course, to use rational numbers ( http://gmplib.org/ ) if you have time to debug why GMP doesn't compile on your processor.
(Although, if you do it for anything else than currency, you probably would do it in base 2 instead of 10. And yes, I know every base is base 10.)