I guess its not customary to tip in department stores per se, but if it were then this example from one hour ago would certainly not qualify

While out yesterday, my wife bought some 'light' shirts and pants for me for next week's cruise, on the basis I could try them and then return/exchange what I didnt want today.

I just took 2 items back and went for a look at what else there was. I asked the sales assistant if there was anything else in similar styles but different colors. She pointed to an area of 'youngsters' clothing, 3/4 length pants etc. etc. I said "I think those are more suited to teenagers". She replied "No they are not, we have them in 'fat bloke' sizes also".
My wife thought it was hysterical. I went to another shop.