Megaventory does not integrate with a service which can process payments from credit cards nor can it be connected with a till machine, yet. As such in order to be able to process payments you need separate hardware (usually a standalone credit card reader) and/or a till machine (for cash).
Megaventory however can work as a POS (ie take in sales over the counter) provided payments are processed elsewhere. The typical Sales/Shipment workflow is used for this functionality.
So you can put up a tablet at your store and ask your employees to fill in the products being sold all in a very simple 3-step, fast process. It is also possible to do this through a barcode scanner too.
Of course, it is also possible to print out right away an invoice to hand to the customer along with the products.
Or login to your account.