Money Requirement Links
The following are some links I have found useful in researching the requirements for how we do financial calculations in Mifos.
http://www.opensourcestrategies.com/ofbiz/ofbiz_bigdecimal_cookbook.txt – There are some ofbiz (an open source business app framework) specific references, but it's mostly a good intro to how to use BigDecimal in financial applications
http://www.xencraft.com/resources/multi-currency.html – A good intro to how to handle multiple currencies in one application. I found the rounding rules section especially illuminating.
http://www2.hursley.ibm.com/decimal/decifaq1.html - Details on decimal arithmetic and keeping scale
http://www.cicc.or.jp/english/hyoujyunka/databook/205.htm - Four Number Rounding rules
http://mifos.org/knowledge/functional-specs/accounting-in-mifos#Rounding_999_account - Rounding rules in Mifos (as of 1.0)
http://docs.sun.com/source/806-3568/ncg_goldberg.html#680 - Info on floating point arithmetic for Computer Scientists
http://mathforum.org/library/drmath/view/63989.html - The bottom description from IBM is a great description of how rounding is handled in financial apps in the US vs. other places.