You should go for a centralized inventory management system which syncs both offline & online sales.
I would recommend you to check out EMERGE App (http://emergeapp.net)
EMERGE App is an order & inventory management with simple accounting cloud software for small companies to boost productivity & drive higher profits Any ...
NetSuite provides a lot of control. Users can be granted more than one role, with each role clearly defining the permissions to view/create/edit records, transactions, reports, etc. The combinations are seemingly endless.