Is it possible to make a point of sale sytem without a barcode scanner/reader etc.. ?

Yes, of course; many *actual* pos systems don't have barcode readers. You just need some sort of screen with big buttons for selling stuff. For instance, hotels don't have barcode readers, because they sell services, not products with serial numbers that can be passed in front of of the POS terminal and scanned. Instead, they just have buttons like "standard room" and digits for entering the amount etc. You can also just let them type in the bar code numbers. Make the barcode entry area activate with a certain keyboard shortcut, and it would work with a barcode scanner when you program it to enter the shortcut itself.