Combine data if same in repeating group

Please have a look at the image.

The price chart is this placed which says how much tax each item has.

Also have order details section where we can see order of a customer with three items.

And at last we can see tax invoice which is a repeating group and displays the tax rate and the items.

The question is how can I combine items in one, if they have exactly the same tax rate.

(In the examples shown above grapes and apple have 2% tax rate so they are displayed in a single row)

group by: Tax rate