How to add an amount + a percentage fee?

I have downloaded the plugin and it seems to be working fine. I was wondering if it would be possible to add a fixed amount (e.g. 25 cents) plus a percentage fee. For example, let’s say a product is 5€ with a flat 25 cents fee and a 2% fee so in the Cart, it would be 5€ + 0.25€ + 0.10€ = 5.35€.

Thanks