I'm not sure it would cause offense if you tried, but Japanese staff would refuse politely if you tried to give them a tip. Tips are not given in Japan, which made things so much more pleasurable and easier I found, not to worry about that sort of thing in return for excellent customer service (I have never had a bad experience)! The only example of a tip that I've seen is at a traditional Geisha house, where people traditionally give smart little envelopes with a bit of money in them as a thank-you to the Geikos for there company.