Originally Posted by AA_EXP09

That is very generous compared to my usual 10% on subtotal.
(for groupon, I use 10% of groupon value plus subtotal of any additional amount, though I usually am good in keeping my order below the amount on the groupon or have very trivial amounts like $1/$3 to add on. Any extra is also not likely to be paid by me, as I can show my order is less than the average value per head.)