Four Square owner Quoc Tran said he had woken about 5am to get things ready for the day ahead.
He had no idea his store had sold the winning powerball ticket until customers began arriving shortly afterwards to check their tickets.
"I had a customer knocking on our door saying 'your store won!' I didn't know what he meant until he said we sold the winning powerball [ticket].
"We've had lots of customers coming in to check if they have the winning ticket, but no. Even I bought a ticket but it didn't win either," he laughed.
Balloons were soon put up outside with a huge sign announcing the store had sold the big $15 million winning ticket.
Mr Tran said the win was even more exciting because he and his wife Thuy Vu and the couple's 7-year-old son had owned the shop for only three months.
He said many people in the town were wondering who the winner was and whether or not it was a local or someone from out of town.
"I feel very excited for whoever has won. It could be a local or someone from Wellington who has a holiday home here.
"I had a customer who said they heard that a couple of people turned up to a cafe in the morning and bought champagne to celebrate.
"The staff over there didn't know what they were celebrating, though."
A staff member at the Drift Cafe on The Beach laughed when approached about the rumour, saying: "Oh, I think that's a bit of Chinese whispers. Obviously everyone's been talking about it and staff were saying this morning to look out for anyone who orders champagne."
The staffer said the $15 million prize was all anyone was talking about in town.
"It is a pretty small community and everyone's hoping it's a local who has won. But it could be someone who is here for the weekend."
Lotteries spokeswoman Karen Jones said last night they were still waiting for the winner to get in touch.
However, it was expected that they would head to Wellington to claim their prize - and it was anticipated they would want to keep their win private.