Marketpress Tax Inclusive Pricing

The Marketpress pricing does not have an option if prices are to be dispayed tax inclusive or tax exclusive.

In Australia anyway we are required to display prices as tax inclusive when selling retail. It is also a requirement to ensure that the tax amount is displayed on the checkout and invoice the customer is sent, so we definitely have to set the tax percentage (which is 10% GST in AU).

From a sellers point of view they would most likely prefer to enter their prices as tax inclusive also.

Is it possible to have this as an admin/settings option, as a simple switch in one of the setup files, or perhaps advise the correct code to go in the template files (but probably best as an admin/setup option).

Would love some guidance how to get the tax setup right. Much thanks in advance.