There is something wrong with "Rounding up with 0.05 intervals (0.06 round to 0.10)".
Test environment: clean installation 3.90
Test product: Fahrenheit 451 by Ray Bradbury
Price with default rounding: 27.00
Price with Rounding up with 0.05... : 27.05
What is more. Add to cart with default rounding looks as below:
While just changing rounding option cause cart would show:
Suddenly sub-total showing as 27.15, shipping rise to 0.05, tax to 0.10, and two discounts are showing just by changing rounding.