Some currencies have no cents or decimals at all on the day to day money exchange. We need an parameter to disable this per currency to which it applies.

I can confirm that yen should have no decimals.
I suppose the only people who deal with fractions of a yen would be foreign currency traders (there is a "sen" which would be the equivalent of USA's "cents", but it is out of use accept for FOREX).

Also applies in Sweden:

you are missing that according to Swedish rules VAT should be rounded and there should be no decimals at all. From a bookkeeping point of view the amount .14 SEK does simply not exist and is being "being left over" when doing the bookkeeping and our auditor is not happy about that...