I've noticed that a lot depends on the way the tape is marked and laid out. My metric tape has a "reminder" printed at every 10 cm, telling you what meter you're working in. But I have to warn folks I'm measuring with that not every place that says "14 m" is the 14 m mark, you have to find the FIRST place where it says 14 and not 13.
With a metric tape I pick the nearest mm, so I record 3 digits after decimal point. With a tape in feet, I find a surveyor's tape marked in tenths of a foot is really handy. You can read the marks to hundredths of a foot, then interpolate to nearest thousandth.
To me the most elusive part about measuring with a steel tape is getting a good temperature reading-- a few degrees difference in temperature can make a surprising amount of difference in length, and in some conditions it's pretty hard to know what temperature to use. I suppose the best is when temps stay pretty steady with no sun shining on the tape.
A few days ago we measured a cal course in Newport News. I almost jumped for joy when we finished, and the recorded temperature throughout was 68 degrees F. Hooray, none of those treacherous temp adjustment calculations!!