Creating an order with multiple non-taxable and taxable products is available in Floranext. Here's how it works.
How to Enable
Navigate to Store Settings > POS Settings > "Tax Per Item" set to YES > Save
Create the Order
On the Take Order screen, once you add the product to the order, make sure the column 'Tax' in the Order Summary section show unchecked.
Also note once enabled, when adding a POS or Website Product, you can choose whether that product should have tax or not by default so you can quickly add common product to an order.