When the controller tells you to keep your code and to contact tower, you should only need to tell tower who you are and maybe which runway you're going to. Everything else has already been communicated via the datablock that's associated with your beacon code on the radar screen.
When you're told to squawk vfr and radar service terminated....when you do contact tower, you'll have to tell them who you are, where you're at, you've got the atis, and what you want.