Hi @AndrewEvans97 I’d be happy to help you with this!
The currency at the final stage of checkout is set by the store and can be changed in your admin under Settings > Store Details. If your customer market is based in Australia, then I recommend setting the store currency to AUD as well. You may need to create a new bank account for your deposits that supports transactions in AUD for this to work. Please note that any instances of ZAR on your store will change to AUD without any conversions. You will need to convert your product prices, shipping rates, etc, yourself if you make this change.
To have the checkout maintain AUD and not switch to ZAR, while maintaining the default store currency as ZAR, can only be done if you are using Shopify Payments. You can learn more about this in our Help Center: Local Currencies.