[FIX] point_of_sale: group products with pricelist
[FIX] point_of_sale: group products with pricelist

Before this fix products in a pricelist would not be grouped when there
is a decimal value in the price.

This problem was caused by a trailing rounding error, for instance a
price of 29.90 could give a pricelist price of 29.900000000002. To solve
this we check if Math.round((price - pricelist-price)/currency-rounding)
gives 0 as a result, if so, the price is equal to the pricelist price
and the product can be grouped.

solves: https://github.com/odoo/odoo/issues/28521#issuecomment-443148920

closes odoo/odoo#29185
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo