If most of the subjects in your frame are on more or less the same plane, then you don't need so much DOF. In this case around f/8 is good for maximum sharpness.
But if you have subjects in the foreground and background, and they are quite far apart, you'll notice how far the DOF goes in the frame. Sometimes the background is not sharp, or sometimes the foreground. In this case you probably need around f/16, more or less depending on the subjects.
If you want to check whether you have enough DOF, have a look at the extreme planes, i.e. extreme foreground or background. If they get sharper when you stop down your aperture, that means you gain in sharpness due to the increased DOF.
If you stop down and you don't get increased sharpness, that means you have enough DOF to cover the entire scene.
Play around with the aperture to see which setting is just right for the particular scene. That way you can maximise the balance between DOF and sharpness.