If you shop at Countdown, looks like it's worth getting a Onecard visa for your shopping. You need to apply for the CC before 20 December to get this.
Usually a $65 annual fee for the card but it's waived for this promotion. Cancel the card after January and buy on a different credit card with airpoints (you get 1.33% back through airpoints on most airpoints CCs, but this only gets you 1.25% at countdown and less outside this promotional period).
Promotion applies to approved applications received between 1 November and 20 December 2015. Eligible spend must be made with your Onecard Visa at Countdown from 1 December 2015 to 31 January 2016 up to a maximum of $5,000.