A debit card used in dip or swipe via a terminal will be free for the retailer - it's processed as an EFTPOS transaction.
So long as you select CHQ or SAV. Selecting CRD will process via Scheme rails, and cost the same as a Debit transaction (and if they're on Interchange+ or Interchange++, will actually cost them more than tapping it would). NZ still doesn't have Least Cost Routing.
Always declines when I choose crd on my debit cards locally, only overseas does that work. I usually would accidentally get the wrong account when at places with paywave but it was disabled just to make them have to do more work.