nextstoplost NZD? Kia Ora!
I'm not sure about the tracking on your site, but as for the currency, this can be a bit tricky at first.
Each Shopify store has a default currency, the currency of the country your store is said to be in...
Since I'm from NZ, my store is 'in' NZ, so the currency is NZD. (Accessed through Shopify Admin Page > Settings > General > Scroll Down.
This is because of the default 'payment provider' (a payment provider is a service that allows people to send money to you) each have their own way of charging you, but since you're in NZ I recommend changing your provider to Stripe (Settings > Payment Providers) and setting the currency to USD.
That way, the main currency of your store will be USD, and you can install an app to show the converted rate to people from other countries.
Let me know if you need more help.