Automatic vocal alignment tools like autotomb (in auto mode) hardly ever produce results that I like... So I manually, and much more cheaply align vocals (when I HAVE TO) with the tools in Reaper, namely a pitch shifter plugin called "ReaPitch". Normally, you would use this plug to ptch something up or down, and let it ride.

By adding an automation envelope that controls the parameters of the plugin you can use it to selectively and precisely tune notes up or down right there on the track in the edit screen in real time.

So, check it out....

Insert ReaPitch on the vocal track, and note the parameters that you can control with it...

When correcting vox, we want to move notes less than a whole note (semitone), what we want to do is move the notes slightly... a perCENTage of the note (cents).

So, now we create an automation envelope that controls the Shift (cents) parameter of ReaPitch.

Click on the "trm" (automation envelopes) button

Brings up the Envelopes control window.
Find the parameters for ReaPitch, and click on the Shift(cents)box. The "visible" and "arm" boxes will automatically get checked. Then close the window.

Now your track has an Automation envelope that controls the Shift (cents) param in ReaPitch. Now, you can create envelope points over the notes that need correcting... (envelope up if the note is flat, and down if the note is sharp.

-Jake