Unable to see Tax in Purchase Orders created

After setting up EB-TAX for specific OU within a country for Payable and Purchasing, we are unable to see Tax being calculated in Purchase Orders created.  When we view the Manage Tax for Purchase Orders the Tax is still 0.00.  This means that the Purchase Order Form will not have tax, only the total cost of items.  The only setup we've performed was:

Defaults and Controls>Application Tax Options

     >Operating Unit = XYZ

     >Application Name = Purchasing

          >Defaulting Order

               >Defaulting Order 1 = Supplier Site

               >Defaulting Order 2 = Supplier

               >Defaulting Order 3 = Ship to Location