Bear in mind that most capacitors have huge tolerances - 20% easily, and electrolytics can be -50,+100%.
This means firstly, that assembling a capacitor from other values may not be as accurate as you expect : if you're trying to get less than a 10% change you may already be there !
Secondly, except in special cases, circuit designers try to avoid a need for accurate capacitance values. So in may cases you can fit something that's 50% out and it will still work OK.