Cryptocurrencies tend to use very large integers (128 or 256 bit) for everything throughout the system. Rounding doesn't happen until a number hits the UI. Why would you design a system that intentionally destroys data several times internally?
Sometimes precision (and thus data) needs to be destroyed. Say you owe me $1,000.211 and write me a check for $1,000.21
Do you still owe me a tenth-of-a-cent?
Even if you do, does anyone (me, you, the taxing authorities) care?
In fact, does anyone want to go through the effort of maintaining that debt?
Even if I repeat this with 100,000 customers, I'm out $100. Again, does anyone care?
> Why would you design a system that intentionally destroys data several times internally?
Because it matches the requirements of the domain being modeled.
Most business to business and business to consumer transactions require that amounts are limited to some number of decimal positions (e.g. in US it's 2 decimal positions).
If you create a system document/transaction like an invoice that doesn't adhere to this rule then your software is not properly modeling the domain (i.e. it's a design flaw).
If you decided to leave it unrounded internally, then you are basically storing an incorrect value and delaying the calculation of the correct value until consumption (which is typically hundreds to thousands of consumers).
But what is the gain to storing the wrong value? Nobody wants it and it just complicates the entire system.
That's usually how it's done in systems using int as well: internal calculations are done with as much precision as needed, and only the significant results are converted back to int using a defined rounding strategy.
