The cashier took a long time to ring him up.
A separate cashier may be the actual person to ring up the payment.
He picked the ring up and stared at it absently, rolling it back and forth between his thumb and index finger.
Thirdly, ask the shopkeeper or ring up the manufacturer.
If I quoted him 1s.9d for American turps he would ring up a competitor in my presence and try to get a better price.
You may even do the same thing waiting for the cashier to ring up the sale.