[FIX] point_of_sale: prevent negative bank payments
[FIX] point_of_sale: use the same rounding sequence as the backend

Conflicts:
	addons/point_of_sale/static/src/js/models.js
[FIX] Fixed the traceback faced when grouping records on the view having computed and non-stored integer/float(ie, fields.Integer(compute='<function>', store=False) field shown(maintenance: 619536).
[FIX] updated the branch to fix the test case 'test_60_read_group'.