Offline PHP POS for Retail

I need a cloud-based point-of-sale system written entirely in PHP that serves a retail shop / supermarket environment. At the counter it should feel as fast as a desktop register, but all data must ultimately live in the cloud so I can monitor sales and inventory from anywhere... (Budget: £20 - £250 GBP, Jobs: Cloud Computing, Database Development, HTML, Laravel, MySQL, PHP, Point of Sale, Software Architecture)