Twice I have asked at banks in Doha, "Can I buy some coins please?" only to be met with looks and tones of total surprise. "Coins? I don't think that we have any. Do we? (to neighbouring teller). No, sorry."

In the supermarket give the cashier three options:
(1) Give the correct change.
(2) Round down to the Riyal below.
(3) Call the manager.
You might be surprised at how quickly they find that small hidden compartment in their cash drawer that is full of 50Dh and 25Dh pieces. (You are unlikely to see the smaller bronze coins)
I am sorry if it affects their income (many are paid only a pittance) but I dislike being given chewing gum in place of change.

Incidentally, a similar announcement to that of UAE was made in Qatar some time ago but has been quickly forgotten.