Speaking of Kiwibank it's worth noting for those who are staying as customers that they start charging foreign conversion fees for overseas payments charged in NZD from tomorrow.

So if you buy something overseas that gives you the option of paying in USD or NZD and select NZD you will pay extra for this. Most of will be aware of DCC and will avoid selecting NZD when offered at a payment terminal, but there are now a huge number of companies online that offer you the option of NZD / USD and use the midmarket rate for their conversions - United Airlines being one such example.

I'm not aware of any other bank in NZ doing this.