Again Sardonic32, you did not read the post.

There is no error, your calculation is wrong. Your calculation is not having the payment costs itself calculated.

you wanna pay 100 euro?,... you have to pay for that 2 euro, yes? So you have to pay actually the fee for 102 euro, which is not 2 anylonger, because it is for 102 and not 100, right? So the fee must be calculated for 102, which is 2.04, so you have to pay 102,04 euro. You could now do the calculation again, but you wont see a difference anylonger due rounding.