Sometimes, but not anyways. Admittedly my sample size is limited to ~3, but asserting my right to decline searches (outside of borders, where you don't get such right), have resulted in 0 searches.
Usually they keep questioning you for a while, but it's not hard to respond in a way that doesn't give them probable cause.
Usually they keep questioning you for a while, but it's not hard to respond in a way that doesn't give them probable cause.