On the face of things, precision seems to always be preferable. For instance, 12.324 is more precise that 12.3. There are times, however, when precision is Not desirable, and may even not make much sense.
Formatting in Excel will make your numbers appear to be rounded. The trouble with relying on formatting is that Excel retains the precision in the background, and any calculations will be based on that precision.
Sometimes precision is the enemy. In such cases, use