How did they explain the 17%? Some kind of luxury rate? And can you explain what you mean about adjusting it to 8% and 3%?
(I still think better to be honest than to be put on a watch list for customs and treated to full examination of all of your belongings every time you enter. And subject to penalty.)
Don't know if this has been posted previously, but it's highly likely you will also lose Global Entry (and TSA pre-check, etc...) if you are caught not declaring purchases.