We are trying to sell the last items. i.e: we have this product with a stock of 19. The 'Group of...' is set to 5, after 3 sells (of 5) we are left over with 4 items. These item's can't be sold because the 'Group of...' is 5.

What we would like to accomplish is a way to sell with a 'Group of...' 5 unless the amount is < the 'Group of...'. With this we would be able to sell the last 4 items of this product. A simple checkbox for this would be great:
"Allow to buy the last stock when the stock is less than the 'Group of...'"