Hi,
HikaShop isn't really meant to be used as a POS.
Most POS system should have either a CSV export of the products or a CSV import of the products data.
HikaShop itself has a CSV export/import system that can be automated.
So normally, when you want to integrate HikaShop with a POS system for the products stock synchronization, you use the CSV export/import system to handle that.
On HikaShop's end, you can automatically export CSVs of the products and either store them locally or send them by email thanks to the mass actions system.
And you can also import CSVs automatically with the mass actions system.
You can read more about the mass actions system here:
www.hikashop.com/support/documentation/167-massaction-form.html
Now it's also possible to develop a custom integration with a POS system but in that case, you need to have a developer work on that for you.
And if you want a POS system which already works with HikaShop, you can look at this:
www.posforwebshops.com/features/webshops