I was working on a heavily government regulated horseracing/gambling mobile website/webapp maybe 7-8 years ago, and we had to prove every intermediate step of a

I was working on a heavily government regulated horseracing/gambling mobile website/webapp maybe 7-8 years ago, and we had to prove every intermediate step of any calculation was done in 1/10,000ths of a cent (or perhaps dollar? It was quite some time ago), and any rounding only ever happened once at the very end. (Where by "prove",they meant "submit the source code" - the "easy" way to get this past the regulators was to have "ten thousandths of a cent" be the base unit of a "custom currency", and only ever convert to dollars/cents in the display code. (Nobody ever questioned the ajax/javascript interaction with the resulting "integer" currency numbers... shudder...) I get the impression back then they everybody in the gaming/gambling industry did this all the time - to the extent that they knew how to organise source code and name variables and functions so the regulators auditing the code would just rubber stamp it. (I was not "in the gaming industry", we were just doing a mobile friendly front end, in jQuery Mobile, to run on the hot new Samsung Galaxy S2... Now I think I need to go curl up in a dark corner and cry myself to sleep again... Project. From. Hell...)