The family, who want to remain anonymous, won the top prize after buying a $10 Gift Pack ticket and couldn't believe their luck.
The mother of the family bought the ticket after doing her grocery shop at Countdown Rotorua on FentonSt. The staff member who sold her the ticket said she had herself been eyeing up the $20 ticket and they had joked about the possibility of winning.
When the mother scratched the ticket at home she was alone and had to call her youngest child to double-check she wasn't mistaken about winning $100,000.
"We were ecstatic," the mother said.
"I rang my husband at work to tell him but he couldn't answer the phone."
The woman took the ticket back to Countdown and the staff member who sold her the ticket said she was kicking herself for not buying it.
The family plan to use half the money to pay off their mortgage and the other half to buy a couple of cars, convert their kitchen and take an overseas trip.
"We're so delighted we can pay off the mortgage and upgrade some things and still have money for a trip overseas," the woman said. "It's a dream come true."