Is retrieving POS cart total before payment possible?

[krishp]

I was going to embark on an app for a specific use case I had but needed the POS sale cart totals before payment.

Reading through the docs, I am getting the impressions that any POS app integrations do not have access to the current POS scanned cart or its total and there appears to be no way to retrieve it until after the sale is finalised and made into a full order in the Shopify back end.

Am I correct in thinking it would be impossible for a sales person to press a button in Shopify's POS and have my server receive the cart total?

My aim is to push the cart total to our 3rd party's PDQ api to prevent keying errors by the team when taking payment, which I can do fairly easily but retrieving the required payment total was my next hurdle.