Display price to include tax

Hi.

Australian Tax regulations say that retailers must show a product's price as inclusive of GST (tax) and show the GST amount on the invoice/receipt.

So, if my client's are entering in their price into the product editing page, they will automatically put the total price, including GST, into the price field. Of course, marketpress only displays the price they enter and then adds the GST on at the point of checkout. The buyer doesn't get to see the GST until they're checking out. This contravenes ATO regulations.

Ideally, this plugin should have a checkbox to say "prices entered are inclusive of TAX" and another one to say "products should display prices including TAX"

What's the best way of hacking this so I can get the products displaying the tax inclusive price?