Retail POS System Development

I need a full-featured Point of Sale system tailored for a small retail shop that scans barcoded products. Every sale, refund, and exchange must be captured with real-time updates to inventory whether staff scan the barcode or add the item manually... (Budget: $15 - $25 AUD, Jobs: .NET, API Development, Cloud Computing, Database Development, JavaScript, MySQL, PHP, Point of Sale, Web Development)