This is, (via) entirely bollocks I’m afraid:

39. 
Never tip with coins that have touched you. If your change is $1.50, you can tell the barmaid to keep the change, but once she has handed it to you, you cannot give it back. To a bartender or cocktail waitress, small change has no value.

Whoever wrote that has obviously never done the job. Quite apart from the fact that four quarters spend just like a dollar bill does it entirely misses the fact that the aim is to get the maximum out of the customer possible while still keeping that customer coming back to do it again.

To which end one bar I used to work in had a great idea. Draft beers were a dollar for a small, $2 for a large. (The place is opposite where the Motley Fool offices are now if there’s anyone interested in updating this for inflation?) However, those were the house prices. On top of that was the 4% State sales tax. $1.04 for a beer, or $2.08 for a large $3.12 for a house mixed etc.

Back then you thought you were doing pretty good if your tips were in the 12-15% range of your sales.  By insisting that to purchase one beer people had to make change (almost no one ever put down less than a dollar and a quarter for a small beer) we were getting 21 cents a beer: well above our target.

Certainly, back then in the mists of the 80s, we bartenders were vastly more aware of the monetary value of small change than our customers were. What to them looked like a small pile of shrapnel, waste to be disregarded, looked to us like something that cumulatively, over the serving of hundreds (even thousands) of drinks in an evening  was a substantial chunk of change (sorry).

I certainly had no problem with clearing the tip jar into the till at the end of the night. $100, $300 in small change contributes nicely to the $200 a night we were each making.