[FIX] account: correctly round amounts to compute matched percentage

Before that, depending on rounding errors on floats, it was possible to end up with a matched percentage of 0.999999999 instead of 1.0 on an account move in case of full reconciliation. This could in turn cause problems with cash basis taxes, when checking what proportion of the move is reconciled.

closes odoo/odoo#44845

X-original-commit: 57c33971
Signed-off-by: oco-odoo <oco-odoo@users.noreply.github.com>