ClarisWorks relies on Apple's SANE code for rounding and other math functions. SANE uses banker's rounding which rounds to the even integer. In a ClarisWorks spreadsheet, if you format column B as a fixed number with 0 decimal places and type in the values in column A below, the values in column B will be displayed.
A B
.5 0
1.5 2
2.5 2
3.5 4
As you can see, Banker's rounding results in alternating between rounding down, then up, then down, then up. This actually results in more even rounding accuracy. However, it is not what most people expect. To always round up from .5, use the ROUND function in ClarisWorks.