I cant seem to find anything useful on this. So here is my problem- I go to a trade fair for 3 days, and I sell things face to face ( I normally only sell wholesale or online via Shopify to end customers at full retail price).My Shopify websotre is synced to ZOHO inventory. My  sales on Shopify come through to Zoho automatically .  At the trade fair I want to have special prices for each item  I  cant just use Shopify POS app because that just gives me all my usual full retail prices from my Shopify website. At the trade show my prices will be  variably discounted and rounded. SO I need a POS app that I can use to integrate with Shopify so my inventory is kept to up to date,  but I can set the item prices to what I want for that particular event. has anyone else done this? 

And  if you have done this, what payment device have you used with this POS app? I thought about using zettle to connect with Shopify ( so I can set prices on zettle) but zettle only sends inventory numbers to Shopify, not sales, so then those sales would not integrate to Zoho inventory...