PrestaShop allows you to configure the price of articles in the catalog by specifying up to six digits after the comma.
It will therefore be possible to specify a price such as €9.123456.
The PayPal module, on the other hand, processes prices by taking into account only two digits after the comma.
For example, a product in your PrestaShop catalog is priced at €9.999.
The PayPal module, in this case "sees" a price of €9.99.
This can lead to differences in the amount when paying for the order.
For example, the purchase of 100 items at €0.899 will equal €89.90.
Whereas, the purchase of 100 items at €0.89 will equal €89.
This difference results in 90 cents difference on the order.
To avoid this type of problem, it is necessary to configure PrestaShop to round the price of each article in the order.
To do this, in the back office of your PrestaShop site, click on the menu item "Preferences" > "General".
Then set the rounding rules as shown in the image below.
Round mode: Round up away from zero
Rounding type: rounding each item
Number of decimals: 2
This configuration is currently mandatory for the PayPal module for PrestaShop to work properly.
A different configuration of these options may cause the module to malfunction due to rounding differences.