Gaussian/banker's rounding in JavaScript

Question

I have been using Math.Round(myNumber, MidpointRounding.ToEven) in C# to do my server-side rounding, however, the user needs to know \'live\' what the result of

Answer 1

Stricly speaking, all of these implementations should handle the case of a negative number of digits to round to.

It is an edge case, but still it would be wise to disallow it (or be very clear about what that means, for example -2 is rounding to the nearest amount of hundreds).