Adding round5() to perform standard rounding, which is now the default

[ddsjoberg]

What changes are proposed in this pull request?
The round5() function has been added and it now used in the default formatters. The round5() does not perform round-to-even, rather the standard type of rounding when 5s round up.

If there is an GitHub issue associated with this pull request, please provide link.
closes #69

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Reviewer Checklist (if item does not apply, mark is as complete)

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