The boundary with 100 does, indeed represent a challenge. However we choose to resolve this particular challenge (I would vote for yes, it's a 3-digit precision, so 105 MUST be rendered as 1.1 x 10^2), the sig figs use in multi-step computation is simple: carry one extra digit without round-off (truncate) in all intermediate steps, and round-off at the end.
What we need is a custom answer checker, or an additional method overlaid on the main one.
Something along the lines of this method.
WeBWorK Problems
multianswer and original_student_ans
This forum has a limit to the number of forum postings you can make in a given time period - this is currently set at 10 posting(s) in 1 day