A Kennedy's Foodcentre trading as Pak'nSave Māngere has been fined more than $70,000 for price discrepancies in 2018.
The supermarket was found to have charged a higher price at the till to what was advertised, or displayed on the shelf.
It had earlier pleaded guilty to six charges of making false or misleading representations about price.
On six dates in 2018, Pak'nSave Māngere was found to have charged a higher price at the till for products like sliced salmon, mushrooms and avocados.
Sliced salmon was displayed at $8.99 but charged at $10.79 on four occasions
Mushrooms were displayed at $4.99 but charged at $6.99 on two occasions
Avocados were displayed at three for $5 but charged at $1.99 each on one occasion.
Those discrepancies were raised with the supermarket by the Commerce Commission, who had sent staff to conduct mystery shops.
Despite this, some were not fixed straight away, and in a written decision, Judge McNaughton described the conduct as repeatedly careless.
"The pricing discrepancies related to a number of individual items across different departments of the supermarket and they were repeated, and the defendant did not immediately take steps to correct its pricing systems," he said.
Judge McNaughton noted that Pak'nSave Māngere did take some steps to remedy the problem but said the immediate failure to act was inexcusable.
Commerce Commission chairperson Anna Rawlings said consumers should be able to trust that the price displayed on the shelf is the one they would be charged.
"If a mistake is made, businesses should ensure consumers are compensated and take immediate steps to ensure that the mistake is not repeated."