You're probably not going to be telling your good party that you're evil and just using them, so anything to help blend in and achieve your goals is a good thing. I constantly use my Chaotic Evil Cleric of Cyric this way, and deception is part of the game plan. I can pretend to be good, if only to better serve my evil god. Now if the thing in question just happens to be something I need for my evil goals, but I can't just tell them, I could simply wait until we rest and steal it while I'm on watch.