Actually they can get mad at you for telling them to have a good day. Some guy started screaming at me to tell him my name when i told him to have a good night. Of course, he had just finished *****ing at me, and i hadnt really been paying attention to his ranting and totally ignored the fact that he had even said anything and went straight to politely sending him on his way by telling him to have a good night, but thats besides the point