In a test shop I added a few products and noticed, that both prices (with tax and without it) were the same - opencart wouldn't calculate the tax, couldn't figure out why.
So, after digging a bit through various settings, entering the relevant geo-zone, zone, tax classes and tax rates and double checked everything was OK, I discovered what was the culprit.
In admin/Tax Rates the relevant Customer group wasn't selected, that's why Opencart wouldn't calculate the taxes ...
And bare in mind: The prices you enter when adding a new product are before tax - net prices!
Hope it helps ...
