I do work for a company that sells many different brands of pos system software.
would marry with your current accounting setup, without any major efforts so in that regard you have a reason to look at them.
Microsoft's POS was designed by a nutty owner of a chain of grocery stores in the US. I won't recommend it to anyone that doesn't fit the model of grocery and loves boring overly complex software. Certainly not a "dollar store" type of retail.
Speaking of running a dollar store, you need to scan items for speed and accuracy but most items are too small, not barcoded, or simply not worth the time to track as they are a one-time order? Most of your sales would be best with pressing a couple large pre-set price keys than anyone can understand in 2 minutes of training? You don't sell anything by weight, and you have no rentals, no tables, no meals to split up?
You can see I'm not a rookie to this..
If I was you I'd look for an open source touch screen based solution. Any solution you look at will have to support exporting data to Quickbooks, but contrary to the Quickbooks support you spoke to, this is more common than rare. Even if going open source doesn't give you a final solution, it will give you all the info you need to find a final solution as you will be aware of what you want/don't want.
If you don't have the resources or skills to implement an open source solution you will want to start looking at demos of the software that the local companies sell. At that point it also becomes interesting as to support options since you're now relying on another company to keep yours running. Now you can see why I suggested open source first.