Does Usave only accept money from R1 coins?

I would like to find out if it part of Shoprite USave's policy not to accept or allow customers to pay with 10,20 or 50 cent coins at a specific time. My nephew was scolded by a cashier at Usave (Crystal Park, Benoni) for coming to buy bread with some of the above-mentioned coins. The cashier proceeded to say to him that he will chase him away next time should he come purchase with such coins. I Find this to be extremely unacceptable and bizarre. I would appreciate an immediate response.