retail counter software with ajax and jquery with mysql database

i want simple software for retail counter there is 1 coloum in one row which is price and then press enter key to second row and then press enter to third row which was also price coloum then if user want to subtotal these row amount and apply discount on these row subtotal so dicount apply then after that press enter to start other row of cloum which is also price coloum then press enter create other column to price and then discount then both subtotal create total then apply final discount then final amount then print this recipte with QR code of these details and when cash counter scan these QR code fetch the invoice no and total amount and the save these in data base please note this this software is working on 3 sec to 5 sec enter key this is very fast process working