Point of Sale Invoice
The one-screen point-of-sale software, for the one-stop-shop retail business. It does everything your store needs, right from POS billing, to purchasing, to customer relationship management.
In the retails business, invoicing needs to done very quickly, hence should less dependency. In the ERPNext, you can create POS Invoices, even when not connected to the internet.
Here is the quick demonstration on the Point of Sale feature of ERPNext.