All orders include 10% GST. You pay no custom duties unless your order is above $1000 AUD.
You'll be responsible for paying duties shipping provider upon delivery. The shipping provider will contact you to settle the final invoice.
You can use the Australian Customs Duty Calculator to get an estimation of any extra fees you may need to pay. Please note that the calculator also calculate import duty on orders under $1000, as import duty will need to be paid if you are importing alcohol or tobacco.