Joomla Virtuemart Point Of Sale (POS) System : Joomla Virtuemart Point Of Sale (POS) System refers to a system where the merchant can create an order from his physical store using the POS and the order will be easily generated at Virtuemart. When you have a physical store and a VirtueMart webshop you can sell your goods with your Point of Sale without giving your sales staff access to the VirtueMart backend. All products/orders/calculation rules/customers will be synchronized into the POS. In this manner, your web store inventory will be synchronized with stock at physical store.
https://joomlashare.ir/categories/extensions/download/138-virtuemart-extensions/406-pos-for-webshops
but not tested with latest version of joomla and virtuemart.