A 10 inch sub is a bit much for 5's, although you do not have to run the sub full last, like Cel said. Generally as my rule of thumb I like to keep a sub close to the size of the woofers.
The question some may say, is why? My theory is by keeping the drivers close you will not have a obvious difference in the lower frequencies. My aim is to not "hear" the sub, meaning to help speakers blend not out do one another.