Tax calculated incorrectly

Hello,

I am using the plugin “WooCOmmerce Discounts Per Payment Method” for customers who are prepaying to give them 2% cash discount.
But that doesn’t work right. The cash discount get detucted from the full price, but not when the Tax get calculated.
So it’s like there is a cash discount of 2% and the price of an article is 150€. So if somebody is buying it and has cash discount, he get 147€. But then the Tax get added and when the Tax gets in it’s using the full price.
So the Tax is 19% and the full price would be 150€ but because of the cahs discount it’s 147€ but the Tax takes 19% from the 150€ and that is the problem.
Why is it like that, and how can I solve that problem?

Thank you.

https://wordpress.org/plugins/woocommerce-payment-discounts/