Change was never a problem, in Morocco. Taxi drivers always had change, restaurants always gave change.
We knew that the taxi should cost 60dirhams from the airport to the town centre, so we withdrew 3100dirhams from the cash machine, so we knew we had enough small notes for the taxi. There is a cafe in the airport, where you could buy a bottle of water to get change if needs be.
The taxi's started trying to charge 150dirhams to go to the town centre, but when we said that it should be 60dirhams, we were bundled in the back of a cab very quickly, presumably so the could continue to fleece other tourists.
I didn't see anything priced in Dollars or Euro's when I was there. Whenever you asked the price it was always in dirhams. There are orange juice sellers, where a glass of orange was 3dirhams, and they always had enough change.