Endgame scoring includes a point for every two food, and a point for every three coins (by default, with some factions scoring varying amounts on the boards' B sides). The rulebook says nothing about how to treat fractional amounts of complete scoring units. Do all incomplete amounts score 0 points, even if you have (for example) 2 of 3 coins towards the next point?
If you get a point for every 3 coins, and you only have 2 coins, then you don't get a point.
In other words, round down. I would suggest that in any case where something says "for every X things..." it should be read as "for every complete set of X things..." -- if the intent is to round up, then it should say something like "for every X things or part thereof...".