This is my absolute BIGGEST pet peeve with servers.  DO NOT ask if I want change....just bring me my change and let me decide!!  Asking if I want my change is asking for a tip....and just plain rude if you ask me!  I always leave a tip....however, if they ask me if I want my change the tip value goes down!!  Generally I tip between 20% & 25%, but when asked about change I leave around 15%.