Let your class create their own money to spend in a class store. Each student designs their own money based on our current monetary system, using decimals through hundredths. Provide a variety of different papers, modeling clay, and other things for them to create with. Discuss the importance of uniformity among pieces with the same value, portability, and perhaps how our current money was designed. Then let students shop in the student store, determine correct change for their purchases, and write receipts for things they have sold. Students can then make a key to explain the value assigned to each piece of their money, attach their receipt, and draw which pieces they used for their purchase and the change they received.