WordPress : Ecommerce solution with multiplier

I’m trying to build a ecommerce website with WordPress.
I know the main ecommerce plugins. The thing is that I need to add somewhere in the dashboard (easily and when we need it) and then to change a multiplier which will change automaticaly all of the prices. For example I want to increase all of my prices to 12%. I will add something like “1,12” and all of the prices will increase to 12%.

And maybe I don’t know if this is possible : Add different products which depend of several rates.
i.e.: I add 3 products within the A category. The category A depend of 3 rates : Shipping, currency rate, inflation.
If I change one of the 3 rates, the 3 products price will change.

Do you know if one of the different plugins do that ?