Supermarket system Based Odoo ERP

I wont A Supermarket System Based Odoo contains basic module Like :
Pos
Inventory
Invoices
...


The main point of Requirements :
- more than one pos in a local server ( I need pos is A fastest)
- in a supermarket some product contain ( Cartoon - peses) two level
- in a purchase bill I wont to allow change of a sell price - this a very important