I just did some checking myself, and the "blue bubble" percentage is displaying exactly what it's always displayed. For example, if it displays "57%," it does *NOT* mean .57%, it means 5.7%, just as before. It hasn't been changed at all, and it is *NOT* possible for mods to now display exp gain accurately to hundredths of a percent.
The "gold bubble" percentage, however, is being rounded. I'm not sure if that's a good or a bad thing. The guild exp percentage has always been rounded, so the change makes everything more consistent; however, as has been extensively noted already, the change also makes accurate tenth-of-percent displays impossible.
-- Darryl (Milquetowst)