Do not show in/excluding tax when items are free

Fixes #2583
@pippinsplugins this one will be tougher to move to the function for free checks, as it requires the price id in the , which doesn't exist until my enhancements are done for #2585 so we have two options here. Leave as 0.00 here, and then update #2585 to do this check correctly, or hold off on this PR until that one is merged into master and then merge master into this with a rebase.