The issue:

Invoices generated in currencies without decimal places may contain decimal places from various calculations (tax, for example) in their total. In some cases this may not be desirable.

Solution:

-Add an option for each currency to set whether or not values should be rounded to the formatted decimals. For example, if the currency format is #,###.## and this option is enabled, round to 2 decimal places. If currency format is #,### and this option is enabled, round to 0 decimal places.-

Add field for each currency to set precision of that currency. Default values to those that match for the currency format.

-Rounding should occur only for invoice total calculations.-

When converting values to decimal format (Currencies::toDecimal), there is a parameter to specify precision, which I believe defaults to 2-decimals places. We should add a new method to fetch the precision for a particular currency so that it can be passed into Currencies::toDecimal and Currencies::toCurrency to override the default precision.

Initial discussion can be found here: http://www.blesta.com/forums/index.php?/topic/979-invoice-rounding-in-different-currency/#entry15852

To update:
This task should update all instances of currency formatting, both for display and for calculation as described in CORE-1581. Currency decimal formatting should always be considered when rounding, and an invoice total would equate to the sum of its rounded line items in the selected currency.