What I learned

It is easier to give than to exchange.
It's tough to stop people and get them to swap. It's easier to stop them and give. "Would you like $1 off your drink?" Some are interested, but nine times out of ten, if it isn't an instant gift of a coupon, they don't want to know.
I trapped two LOL going into Main Squeeze. "Would you like a dollar off your purchase?". "No, we're just going to get some soup". ???!! "You can get a dollar off just by exchanging five dollars for five dollars". No, sorry. They smile and move in.

Giving can be a mistake
When you hand out $1 or $5 in an unusual currency, people treat it as worthless. They find it hard to believe that it is worth $1.
I feel the same way.
I'll hand out $T1 quite happily, but wouldn't dream of tossing a loonie in a busker's hat, and yet I enjoy the clarinet and the violin.

Giving can be a mistake
I gave $T5 to a handyman who had been busy next door for an hour. He asked what it was, I told him and suggested he refresh himself, on me. He darted back out of The Main Squeeze and grabbed a second $5 from my hand; "Gimme another; I just gave mine to my client.
I was struck dumb. I'm down ten of my dollars; he has made a good impression on his client. The Main Squeeze made $30 off him.