We encountered a problem with payments when rounded, the amount paid is actually different from the amount confirmed, this gave us the error on orders where the status would be Payment Failed due to a 2c difference.
To fix this we changed the 2 to a 3 on this line in defines.inc.php
define('_PS_PRICE_DISPLAY_PRECISION_', 3);
But now all of our products are listed with 3 decimal places, like €9.990.
Is there a better solution?
David