Some documentation is already there on internal representation of numbers in ledger. It stores numbers as rational numbers avoid rounding problems arising of floating point representation.
The only time when rounding occurs is while displaying. But there are some other rounding problems in accountancy and it will be good to have a discussion on them.
From the point of view of accountants,
1. Control over displayed precision
There is no option to force a desired display precision. There is no option to increase or decrease display precision via command line.