I totally agree with Bluebelle, I don't really agree with tipping. It enables employers to pay lower wages and in the case of a service charge which is added to the bill, I have heard it will not find it's way back to the staff but is used to pay wages (heard this on Watchdog from a member of staff of a restaurant speaking undercover.) Bluebelle is right, why would I tip a taxi driver but not a bus driver? I do round up my hairdresser's fee, she charges £43 for a colour, cut, and blow dry which I think is very cheap, I round it up to £45 (she is very good too and has been cutting my hair for many years.)
I wouldn't tip generally, it's outdated, and was originally 'to ensure promptitude' which meant the tip was given before the service to ensure the tipper was served first.