rounding up XP expenditures

Where is the rule that XP expenditures are rounded up? I saw this in an earlier thread in reference to Secondary Insight, or Affinities, or something... help?

IMHO, if nothing else is mentioned in the game system, you use normal rounding rules. Below 0,5 rounds down, 05 or above rounds up. A system like GURPS specifically rounds down.

Only specific reference I can recall is that Affinity (Ability) specifically states that you round up.

And isn't Affinity the only thing were you'd end up with fcations of xp? Elementalist and Secondary Insight give full xp in bonus, right?

So I believe.