Taint and Honor were both converted from the d10 system to the d20 in an inellegent fashion. In the d10 system there are taint points and taint rank. Every 10 taint points ups you a taint rank. So, if my poor Matsu Bushi had a taint of 3.6, she would have 3 ranks of taint and 6 points on top of that. 4 more points would get her to rank 4.
I suspect that this is why OA has a 10-point scale (based on rank) and Rokugan has a 90-point scale (based on point). Without fractions, characters using the OA version are going to be in trouble pretty fast, so I use the version presented in Rokugan (Actually, I use it /10 just like in the d10 system, so it's a 4.5, not 45. It's easy enough to convert).
Honor works much the same way in the d10 system and I adjusted the d20 to reflect this. Most starting Crane characters, for example, have an Honor of 3.5 (eqv). Honor losses and gains are by 0.1 increments, barring something truly epic. The 2nd edition Player's Guide for the d10 system has a clan-by-clan chart for honor losses and gains, since it stands to reason a Mantis and a Crane will have different standards.