In the setup section of your sketch (or anywhere, really, but I like setup as setting the register is definitely part of setting the thing up), put this line in:
OSCCAL = 0x4A //Set the clock calibration
Replace the 0x4A with whatever Tinytuner spits out as a calibration value.
Plus side: Your attiny is now running with a decently accurate clock.
Minus side: You have to do this for each individual chip, every MCU's oscillator is out to lunch in a random direction, the value that works perfectly for one attiny84 may give you a clock completely out to lunch in another attiny84. Most likely, in fact.
So if you put the same code on multiple chips you'll have to edit the calibration line in the sketch to match the MCU.