[GNC] Looking for Point-of-Sale App suggestions & if any interface with GnuCash & How

[Fran_3]

1 - What Point of Sale Apps would you sugges for a small business?(Open Source is preferred.)
2 - Do any interface or transfer data easily with GnuCash?
3 - If so what info does the POS software share?.. daily sales.. sales by item with sales by quantity and total sales dollars and/or price of each item sold... or what?
4 - How does the POS software share data with GnuCash?.. export CSV file to be imported by GnuCash.. or what?
Thanks for any help.