Senior Constable Chris Blackford, of Queenstown, said in Frankton the man ordered items to the value of $2.60.
After receiving $97.40 in change, the man told the cashier he had the $2.60 in change and requested the $100 back.
He short-changed the cashier by handing over only $37.30 before quickly leaving.
Sgt Paget said the man had been caught out in Kaikoura by a worker who had been warned about the scam. When challenged, the man returned the money.
Sgt Paget said police knew of only those three places that had been affected, though there could be more.
''We don't expect a repeat in this area but it's a bit of a wake-up call for cashiers ... to be aware that not everyone is honest.''
The man is thought to be driving a white rental hatchback, hired in Auckland, and to be travelling north.
Police are investigating the incidents and believe they have some leads.