It is all about precision
Sometimes close is good enough and other times you need precision. You can either set Pentacalc to auto-select how many decimal places to show or you can set it to show up to 15 decimal places.
Your calculator your decision
PentaCalc Pro offers four different display options (in the Option menu):
If you select either Fixed, Scientific, or Engineering, a dialog box will appear requesting the number of decimal places between 0 and 15. By rounding only in the display, PentaCalc minimizes rounding errors throughout your calculations