Seems like Money type is discouraged as described here.
My application needs to store currency, which datatype shall I be using? Numeric, Money or FLOAT?
Numeric with forced 2 units precision. Never use float or float like datatype to represent currency because if you do, people are going to be unhappy when the financial report's bottom line figure is incorrect by + or - a few dollars.
The money type is just left in for historical reasons as far as I can tell.
Take this as an example: 1 Iranian Rial equals 0.000030 United States Dollars. If you use fewer than 5 fractional digits then 1 IRR will be rounded to 0 USD after conversion. I know we're splitting rials here, but I think that when dealing with money you can never be too safe.