Converting a price can leave awkward numbers like 1,847.23. Rounding tidies the converted price shoppers see, so prices feel intentional.
The rules
None keeps the converted amount as-is. Round up or Round down moves to the next whole unit. Nearest .99, .95, or .50 snaps to the closest ending. Nearest whole rounds to the closest whole number. Rounding only changes the converted price shoppers see; your base-currency prices stay untouched.
Setting it
Each additional currency has its own rule. Choose it while editing the currency in manual mode, or from the rounding selector in automatic mode. The base currency never rounds because it's the source of truth.