This PowerPoint is perfect for test prep! It reviews all the key concepts associated with rounding as outlined by the Common Core State Standard 4.NF.C.7.
For the "practice" pages, I like to "model" with the first set of problems and then have students work with a partner for the "guided" section. Finally, they work "independently." Then, I repeat the same process for the second row of boxes. This way- you're slowly scaffolding your approach to releasing them to do their own work.