Use currency and monetary so that rounding will be done by the ORM*

add new line Pylint

fix pylint

pos_payment_change/wizards/pos_payment_change_wizard_new_line.py

@@ -20,7 +20,15 @@ class PosPaymentChangeWizardLine(models.TransientModel):
         domain=lambda s: s._domain_new_journal_id(),
     )
 
-    amount = fields.Float(string="Amount", required=True)
+    company_currency_id = fields.Many2one(
+                            comodel_name='res.currency', store=True,
+                            related='new_journal_id.currency_id',
+                            string="Company Currency", readonly=True,
+                            help='Utility field to express amount currency')
+
+    amount = fields.Monetary(string="Amount",
+                            required=True, default=0.0,
+                            currency_field='company_currency_id')
 
     @api.model
     def _domain_new_journal_id(self):

pos_payment_change/wizards/pos_payment_change_wizard_old_line.py

@@ -19,5 +19,13 @@ class PosPaymentChangeWizardOldLine(models.TransientModel):
         required=True,
         readonly=True,
     )
+    
+    company_currency_id = fields.Many2one(
+                            comodel_name='res.currency', store=True,
+                            related='old_journal_id.currency_id',
+                            string="Company Currency", readonly=True,
+                            help='Utility field to express amount currency')
 
-    amount = fields.Float(string="Amount", required=True, readonly=True)
+    amount = fields.Monetary(string="Amount", required=True,
+                             readonly=True, default=0.0, 
+                             currency_field='company_currency_id')