Point of Sale Solutions for a tech savy company

I am in the process of opening a retail establishment. I am personally developing a phone app and website which will interface with a mysql database to display certain relevant information about our current inventory to our customers. I would also like to have as much data as possible about when sales occurred, how much was spent, what product was purchased, credit card or email address of purchaser, etc, available for business analytics purposes. I am interested in finding a POS system which essentially databases every transaction that happens in a way that I can externally (i.e. not having to run the software itself) access this database to either present the pertinent portion of this data to my customers or analyse this data for business planning purposes. It is also essential that my employees can interact with this system without any more computer expertise than it takes to run a McDonald's cash register and that my customers can interact with the system without any more computer expertise than it takes to walk through my front door. Does anyone have a POS solution that will satisfy these criteria?