my 5year old

My middle child is 5 and im having issues with him listening. example we were at the mall to buy him shorts. He was wearing sweatpants and i told him to go change into the shorts. He didnt want to so he stood there silent while i had kept trying to convince him. He jist kept saying no no no over. Finally i got him to change. At home when he gets into trouble I PUT HIM IN TIMEOUT in his room for 5mins. but he doesnt go willing. Ill even count to three cause it use to work. i have to carry him to time out. when it comes the clean up he somehow manages to slack and convince his sister to do it all. I just dont know what to do. Like he smiles when hes in trouble he thinks its funny. like what do i do. Hes fine at school. at grandmas and grandpas but no where else. like he'll throw fits anywhere. resturant. supermarket. etc