Since the beginning of time — or at least the beginning of the movie Reservoir Dogs — people have debated the proper amount to tip. There are no hard and fast rules for how much you need to tip for various services, and it comes down to a matter of personal preferences as they relate to social customs. Few people really like paying more than they need to be, or to be viewed as a cheapskate, so everyone walks a fine line when deciding how much to leave.
If you’re a mailman, you’ll probably look just a little more kindly upon those who slip you $10 gift cards during the holidays, and may be willing to work just a little bit harder to keep them happy throughout the year. So think of holiday tipping as a way to buy goodwill that lasts year round and you’ll find yourself more motivated to tip appropriately.