Can you believe that I worked in a paint store for almost 6 years and I have the exact same problem with the tape. I have a fool proof way of achieving the perfect seam between walls without the hassle! It is simple. Paint your usual method as close as possible to the edges. Purchase a small artists brush and finish off the edges. It will take you a little extra time to complete the job but I can guarantee you it is worth it. And make sure that you don't skimp on the artists brush. Buy a decent quality brush so that the bristles lie straight. I prefer a 1 inch brush. Good luck!

paint the lightest colour first have it run slightly over where the new colour is going to start then apply your tape after it has dried for 24 hours. Then paint along the tape with the lightest colour this will seal the tape line and stop any bleeding. then apply your next colour. When you peel the tape off there will be no paint bleeding it works great I used this for colour blocking my wall and painting lines etc. works like a dream every time...