I often use the following.
Say your song from sheet music is 32 bars long. I set the song length to 31 bars and BIAB adds by default an extra two bars at the end. So I now enter the last chord in the song in the first of those ending bars and add three dots after it. For example if the last chord in the song is say an E, put E… (three dots after the chord name). (Note if BIAB happens to put in the wrong chord in the first of the last two bars just change it ). Now when the song is played back the whole band when it reaches that last chord (in bar 32)in the song will play that chord and stop.

You can also add a slow-down say from the second last bar by typing F5 and enter a tempo which is say some value smaller than the tempo of the song by trial and error.
This is often indicated in the sheet music as a “rall.” And can make for a nice ending.