AFAIK its perfectly legal here in UK as well, although the EPOS terminal would have to be reprogrammed to reflect this as a discount or the cash ledger isn't going to reconcile correctly and Her Majesty's Revenue and Customs might ask questions, and we currently have a surplus rather than a shortage of coins (as just about everywhere accepts electronic card payments so cash use in shops is rarer, I only keep coins to occasionally feed parking meters)
Also most countries have laws that only allow you to pay up to a certain quantity incoins and any more is excplicitly not considered legal tender. Non-legal tender are considered commodities most likely and while you can still trade commodities for good it falls under different tax laws and thus strictly speaking a cashier could not take it unless taking some extra steps at a minimum.
Australia, UK, Ireland, and India are 4 countries I know of off hand that limit the number of coins per-purchase for legal tender purposes.
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