Hello again Milbo
I have tried some settings and have found that as soon as the final price has more than 2 decimals, You get a discounted price

You can see the images illustrate the following.
Round-display-only-error-discount-01.jpg (settings for file 01 - 05)
Round-display-only-error-no-discount-02.jpg (no discounted price)
Round-display-only-error-no-discount-03.jpg (product price)
Round-display-only-error-discount-04.jpg (discounted price)
Round-display-only-error-discount-05.jpg (product price)
If I check the option
Round only display, I get:
Round-all-no-error_no-discount-11.jpg (settings for file 11-15)
Round-all-no-error_no-discount-12.jpg (no discounted price)
Round-all-no-error_no-discount-13.jpg (product price)
Round-all-no-error_no-discount-14.jpg (no discounted price)
Round-all-no-error_no-discount-15.jpg (product price)
It looks as far as I can see right now, that I don´t get any unwanted discounts when I turn off
Round only display.
If this is the solution to the problem, then it would be great

regards
Jörgen @ Kreativ Fotografi