Magic Tip Jar is a feature for the players reached ??? CpS. Every time you open it, the cost is $2.99, getting all Rainbow Cookies in the jar to reset to 300.
In addition, 20,000 is added to its capacity.
Tip Jar Bonus Edit
The more often you open, the bigger your Bonus!
Each time you open the jar, you'll get +10% bonus amount of Rainbow Cookies the next time you open it.
In Version 4, there can be limited amount of cookies inside the jar, starting at 80,000.