The principle is that you have to round so that it contains only sig. fig.
Sig. fig. : the certain values and the 1st uncertain value
In case you are measuing a solution in a buret, as i know the buret has an error of +/- 0.02, here there is 2 certain digits and 1 uncertain (3 sig. fig.)!
the uncertain 1 is the last digit and the certain are the 1st 2
if you have 400 and there are 3 sig. fig., which are the certain digists and uncertain values?
if you have 450...2 diffrent cases, in the first is +/-10 and in the 2nd case +/-2..same question!
Do this, Good luck:)!