I am working on a d100 homebrew game, and I'd like to include the mechanic where under certain conditions (such as a critical hit) you flip the digits (so a 30 becomes an 03). I'm trying to remember how games that use this 'flip the digit' mechanic handle things when you roll a 100. Does a roll of 100 ("00" and "0") remains a 100 even when flipped? What's the best way to handle that?  I seem to recall Warhammer Fantasy RPG doing this but I don't have access to the rulebooks at present.