[FIX] pos_cash_rounding : Unpaid orders when using cash rounding

Current behavior :
When using cash rouding method "HALF-UP" if the difference between the rounded price and the original price was exactly the half of the cash rounding, the order would appear as unpaid.

Steps to reproduce :
- Create a rounding method of 0.5 (half-up)
- Sell a product for 11.25
- The order appears unpaid in the PoS orders list view

opw-2593687

closes odoo/odoo#81747

X-original-commit: 43a20a62
Signed-off-by: Grazioso Andrea (agr) <agr@odoo.com>
Signed-off-by: Engels Robin (roen) <roen@odoo.com>