All teachers know the significance of error analysis.
Most of us have difficulty with the slip-shod manner of using significant figures as a treatment of error analysis. The printout of a solution from the Homework Service's algorithms is computer output. It is more sophisticated than a hand calculator, but the idea is similar. If we were to eliminate devices that give results of calculations with digits past the significance of the values that they represent, then we would not use calculators or computers for our theoretical calculations. It is nonsense to limit the precision of a calculation.