Fixed round implementation support for numbers that have string representations that use exponential notation.

[sflanker]

Resolves #5340

Changes:

The round() function now uses multiplication and division by powers of 10 to implement rounding to a fixed number of decimal places instead of using string concatenation with exponent notation.

PR Checklist

• npm run lint passes
• [Unit tests] are included / update

[outofambit]

this looks great to me! thank you for writing additional tests :)

i'll wait a couple days to merge so others can chime in if they have any concerns

[limzykenneth]

Only potential edge case I can see is that if n * multiplier is larger than what can be represented by JS Number it may give an unexpected outcome. Ignoring that, this is ok to merge.