This question already has an answer here:
if I want to add a new Product (sale price 39,99) I can set the price like this: 33,60504201680672 (without tax).
The price in the shop is now shown correct: 39,99.
If I edit then the product, the price is in backend 33,61 and in frontend 40,00.
I already set the rounding decimal place in Store.php from 2 up to 4.
The Magento version is 18.104.22.168.
Can anybody help?