I have setup my store for Australia. The procedure i followed is this Setting store for Australia
According to this : To set tax correctly for Australia (prices shown include GST) and to apply discounts correctly, the following should be set: System → Configuration → Tax Tax Classes
Tax Class for Shipping = Shipping
Tax Based On = Shipping Address Catalog prices include tax = Yes Shipping prices include tax = Yes Apply Tax After Discount = Yes Apply Discount On Prices Including Tax = Yes Apply Tax On = Custom price if available
Default Tax Destination Calculation
Default Country = Australia
Display Cart/Order Prices = Including tax Display full tax summary = No Display Shipping Prices = Including tax Display Product Prices = Including tax
But i couldn't get text "incl GST" after price in product detail.