openTRANS: line amount rounding issue

[mgesing]

Due to rounding, the unit price multiplied by the quantity of the exported values does not add up to the line amount. Example

	Value	Export value
Quantity	2	2
Unit price	122.1667	122.17
Line amount	244.3333	244.33

Consider generally exporting unrounded amounts (4 decimal places), which should be ok for the NUMBER format according to the openTRANS specification. See ExportXmlHelper.