And don't try and fiddle the taxi times either. It really does piss the Captain off if they discover an enterprising little turd has been logging you off chocks early and on chocks later than you actually are.
On a spritely turn round you get the question how did you mange to come off chokes on your third sector before you came on chocks for your second from ops. And I always round down at the start to nearest 5 and up for on chocks is cheating as well.
Your company may have permission from thier flight ops inspector for you to log block hours. Its a fiddle to make it easier to work out roster FTL's. Again cheating if you ask me. And dodgy as hell if they are doing it with Airframe hours