If it benefits you rounded down, if not rounded up
There's no clean rule for that, but usually decimal digits are truncated. Anything after the decimal point is just discarded. So for example 5.99 would be "rounded down" to 5 while -5.99 would be "rounded up" to -5. (On the technical side, the game usually just casts floats/doubles into ints.)But there are exceptions, and AP cost is one of them. You can check the AP cost tables at https://www.underrail.com/wiki/index.php?title=DexterityWorth noting: if you calculate stuff by hand, the in-game math can be off by one from calculator results due to floating point rounding errors. Usually this won't matter, but with thresholds like AP costs or crafting skill requirements that one point could make all the difference.