Thank you for reaching out and posting this question!
I understand you're looking for an app that supports discount stacking on the Shopify POS for your retro video game store. Since you need an app that supports Shopify POS, then that does help us narrow down the options. With that being said, I'd recommend taking a look at Stackable Discounts or All In One Automatic Discounts. Both of these apps support the Shopify POS and the ability to stack multiple discounts. If you need any help with either of these apps, then the app developers are always available to assist you - you can reach out to them directly through the contact information in the Support section of their app pages.
I'd love to hear more about your business! Does your business sell online? How are you finding our platform for your retail store?
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Thank you for your response. I have already tried Stackable Discounts, but unfortunatley in order to use thier discounts for POS I have to have Shopify PRO which at this time does not warant the extra cost.
I will however try All In One to see how it works.
As for my business, yes we do also sell online ( classic-controller.com). This is one of the things I love about Shopify. The fact that I can both use Shopify for my POS and automatically use as a website.
I will ley you know if All In One is for me. Thanks again