To the
OP,
If you have only clicked on "Buy It Now" you can simply exit the transaction at any point, up until you click on "Commit to Buy."
If you've done that, hen you will need to contact the. Seller and ask them to cancel he deal. Most will do so rather than trying to chase you for payment.
When shopping on ebay USA, you can sometimes flick I back to Aus, just by inserting the ".au" into the address bar.
It really is simpler to shop on the au site, and simply change the location 5o worldwide. Anything listed on the USA site, by a seller who ships to Aus, will show up in your searches.
Plus the au site will collect the GST and save mucking about.
Note that if using a credit or debit card to pay via Paypal, you can choose to keep the transaction in USD, and let your bank do the conversion instead of PayPal