How to apply Tax/Fees % on total amount during checkout

Hi,
My Store is mygamingedge.net and I am running Opencart 1.5.5.1.

I want to apply certain amount of fees or tax in percentage on the total checkout value.

Firstly, I tried using TAX system and I made a tax class "Default 3.9%"http://gyazo.com/fedea9e403950ecab0f0e11721e3a928.

and I also created a Tax Rate for it http://gyazo.com/d3e9cd72fe3f836205c3cdbc80b15465.

But somehow it doesnt seem to work when I set the tax class to any product.

I noticed you selected to base taxes on your store address. I'm assuming your store address is within the UK Shipping geo zone?

Also double check that you have the Tax order total extension enabled under:
Admin CP > Extensions > Order Totals > Tax


Regards,
Joel.

I have this same issue. I'm in the US though. I can't find where to change what shows up as a GeoZone though. (if that is needed for the tax to work)

Geo zones are created in System > Localisation > Geo Zones. You can then apply them to tax classes, payment methods, shipping methods, etc.