If you are building a business regarding on having bitcoin payments or prices then its quiet a bit of hassle.You could do both options ex. setting the exact amount of bitcoin on exact dollar price that you would like to put the risk of having profit or negative is always there thats why make some allowances ahead on profit but dont put too much since it would be already expensive just put up a competitive price.Actually i cant illustrate furthermore because i dont have any intentions to have business out of bitcoin because of fluctuations.