I made a new thread for this post as to not confuse it with the previous post since there was no info there about the update that got it working. I have done some testing of the USPS shipping that is provided in PowerStore and I can confirm that you should see a shipping charge on the confirm page if you have done the following:
You have filled out the settings for the shipping in the admin section of your PowerStore.
The items that you are working with have a weight specified for them.
The shipping enabled checkbox is checked in the admin.
Check all of these settings and let us know if you have any trouble with them. If the issue persists please let us know so that we can look into this further with you.