Refusal of a coin

When wanting to pay for my goods at the store, I took out some coins and gave it to the cashier ( three R5 coins and a R2 coin). The cashier then grabbed a different R5 coin out of my hand and gave me a R5 coin that I had initially given her. She sad "I don't want this one". I hadn't noticed the scratches on the coin and was taken by surprise that the cashier refused my money. Money that is legal tender! The manager gave an excuse that she is busy when I asked to see her. The last time I checked, retailers have no right to refuse a coin or note from a customer, unless it's the old R200 note.