Estimated Shipping & Tax

How would I change the prices in the box that comes up on the shopping cart page to estimate shipping so that it says after the exc tax price the inc tax price? It says the inc tax price once you select a shipping method but I think our customers may be confused about why the price changes.

So basically I want (for example):

[center]Registered Post (3-5 Business days) - $7.95 ($8.75 inc GST)[/center]