HP calculators will only display the number of digits you specify and there is an RND function which will round the number to that number of digits. While it d

HP calculators will only display the number of digits you specify and there is an RND function which will round the number to that number of digits. While it doesn't fulfill the criteria of "managing significant digits" (you still have to know at each point how many significant digits you have, which isn't obvious with calculations like logarithms), it does make things significantly (ahem) easier in most common cases.