This is a figure taken from "The effect of trailing end geometry on the vibration of a circular cantilevered rod in nominally axial flow" by M.W. Wambsganssa and J.A. Jendrzejczyka.

What is shows is that for a tapered trailing edge, the angle between the two sides of the taper needs to be about 30 degrees or less for there to be a low level of induced vibrations (that can lead to larger vibrations known as flutter). A taper with an angle of 60 degrees is actually over 3 times worse than a simple flat (blunt) end and a rounded end is over 2 times worse than a blunt end. A sharp taper is not only fast, it is much less likely to flutter (which are both related, because vibrations means that there is turbulence - which is drag - which is wasted energy).

Bob