POS integration for retail chain — sync sales, stock and prices

We operate a growing retail chain with several physical stores plus an online shop, and today our sales data lives in disconnected islands. Each cash register records transactions locally, the web store keeps its own catalog, and our warehouse spreadsheet is updated by hand at the end of the week. The result is oversold items, mismatched prices between locations, and hours wasted reconciling numbers that should simply agree. We are looking for an experienced developer or team to build a reliable integration between our point-of-sale terminals, the online store, and the central inventory so that everything talks to each other in near real time.

The core of the job is two-way synchronization. When a cashier rings up a sale in any location, stock levels must drop everywhere instantly, and when an online order comes in, the same shelves must reflect it. Prices and promotions edited in one place should propagate to every register and to the website without manual re-entry. We also need clean electronic receipts issued at checkout and consolidated daily reports that show revenue, returns, and remaining stock per store and per SKU. Please tell us which POS hardware and platforms you have integrated before, how you handle connectivity drops at the counter, and your approach to keeping data consistent when several locations write at once.

— Two-way sync of sales, stock and prices across all stores and the website
— Electronic receipts at checkout and consolidated daily reports
— Offline-safe queue so terminals keep working during connectivity drops
— Clear documentation and handover for our staff