Let your students use plastic change to "buy" products. Group you students into small groups. Assign one student in each group to be the cashier. The other students are consumers and have to work together to count the correct change. The cashier double checks the change then lets the teacher know that they are finished. The teacher then triple checks and gives out stickers if it is correct for the sticker chart. This worked great in my classroom and I hope it works great for you, too.