Melika77,
From what I've read here and elsewhere, I believe most people tip $10 each way just in case they get a different driver. What you tip, though, is entirely up to you.
Have fun! Tiffany Towncar really does do a good job. We hired one of their vans this past December, and couldn't have been happier. Of course, we were in Orlando, so that might have had something to do with it. (wink)
Inky
17 days and counting (again)