Config : It is under shopper groups.  In the back end under Shopper click on List Shopper Groups.  Then click on the shopper group or groups that are published.  Uncheck the option to "Show Prices including tax". 

Hack : Change two files

1.Change the following code from "components\com_virtuemart\themes\default\templates\basket" :- in line 72-77

ERROR [include_code_listing plugin]: File Not Found (C:/Inetpub/vhosts/joomlavm.com/httpdocs/display codes/tax1.txt)

2.Change the following code from "ro_basket.php"

ERROR [include_code_listing plugin]: File Not Found (C:/Inetpub/vhosts/joomlavm.com/httpdocs/display codes/tax2.txt)