One of the "calculator challenges" is that students often don't know how to use the calculator (or spreadsheet) efficiently. Writing down intermediate answers, and then re-keying them for the next step of the calculation will inevitably propagate truncation errors through the operation.
I encourage students to use calculator memory to store intermediate results for retrieval in subsequent stages.
I do, however, fall into the school of asking that students round the final result appropriately, with the understanding that those digits in the answer which are to the right of the uncertainty are effectively noise.
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"When I hear about Schrödinger's cat, I reach for my gun."
-- Stephen Hawking
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Dr. George Spagna
Physics Department
Randolph-Macon College
P.O. Box 5005
Ashland, VA 23005-5505