add aruban florin cash rounding

[Testsubject1683]

according to wikipedia, the smallest coin available is 5 cents https://en.wikipedia.org/wiki/Aruban_florin

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This change is 

[Testsubject1683]

Fix for https://github.com/JavaMoney/jsr354-ri/issues/407

@keilw can you please have a look?

[keilw]

Thanks, will do when I get to.