Do your students already know how to multiply by 5s and 10s? Does your district calendar give you a whole day to teach 5s and 10s?
These are cards you can print out for Quiz Quiz Trade Kagan Cooperative Learning Games. They make the students practice their facts without making them do silly worksheets on topcis they already know.
I did this with my gifted 3rd graders and they loved it! After a short explicit lesson on multiplying by 5s and 10s, my students were ready to practice their facts.