BEags
Depends what you mean by "to the nearest farthing".
5/6½d (five and sixpence ha'penny) a pound is the nearest to the exact answer, but realises slightly less than 10%. To the nearest farthing producing
at least 10% (in fact slightly more than) you would need to charge 5/6¾d (five and sixpence three farthings) a pound.
