Steps to Reproduce Bug: - Create PO - Remove default Currency - Add a Line Bug: ```ValueError: Expected singleton: res.currency()``` With this Commit, we are using default currency to round amount. closes odoo/odoo#74234 X-original-commit: d9ff2e8ec7200aa15830e92e5083251c4e81dd1c Signed-off-by: Arnold Moyaux <amoyaux@users.noreply.github.com>