Customer Management System with API

We need a shopping cart system that integrates with the front end of our website in order to allow customers to register directly and then order items and be given points for every dollar they spend before taxes calculated in their profile so when they log in, they can check the status. We will also need to record a 12digit number to each clients profile as reference to their customer card. We will need to have an API developed for it as well in order to integrate with our instore POS system.