In our country, taxes are included in the price. Every month we declare the revenue on which we pay 13% VAT rounded without decimal. Example

revenues: 98
13%: 12.74, rounded to 13

Odoo's cash rounding rules allow you to round off the total of the invoice but what we need is to be able to round off the tax accounting items, and therefore that of the untaxed price. The total invoiced can have two decimals, only the tax amount must be rounded to the lower unit (if the decimals are up to 0.5) or to the higher one (between 0.51 and 0.99).

The simplest way to do this is to rewrite the amounts in the "other information" tab of the invoice. But I wanted to know if there is a way to do this automatically. Looking around I saw that maybe you could write some calculation rules in the corresponding field (I think it is amount_tax but I'm not sure and moreover I don't know how to do it). Anyone have or had similar problems? Thanks