In Pathfinder Society Organized Play, it is possible to play a character using the slow experience for one of its level. In that case the experience needed to level up doesn’t change, it’s the experience gained that change from 1 XP per scenario to 0.5 XP.
I tried to add that XP to the character and it doesn’t seem to work. It would be good to allow decimal XP.
For some reason I seem to remember having used PCGen a long time ago for dnd and used decimal XP (only one or two numbers after the dot). I’m probably remember incorrectly.