Thank you for your answer.
The problem is not the 2 decimals places required but the check made from the plugin adding the items. This is an example taken from the logs file:
[L_PAYMENTREQUEST_0_NAME0] => product1
[L_PAYMENTREQUEST_0_AMT0] => 5.25
[L_PAYMENTREQUEST_0_QTY0] => 42
[L_PAYMENTREQUEST_0_NAME1] => product2
[L_PAYMENTREQUEST_0_AMT1] => 3.26
[L_PAYMENTREQUEST_0_QTY1] => 126
[L_PAYMENTREQUEST_0_NAME2] => product3
[L_PAYMENTREQUEST_0_AMT2] => 3.13
[L_PAYMENTREQUEST_0_QTY2] => 126
(5.25*42)+(3.26*126)+(3.13*126) =1025.64 <<<total
[PAYMENTREQUEST_0_ITEMAMT] => 1025.38 <<<total calculated starting from the unit price with 4 decimal places and rounded to 2 decimal places
1025.38 != 1025.64 so “The totals of the cart item amounts do not match order amounts”
Is there the possibility to bypass the calculation and send to Paypal only the total?
Thank you in advance