Cannot upgrade to iTunes 10 due to OS X 10.4 - Help!

I'm so annoyed with Apple right now, but I guess that's not a new sentiment for a lot of people. Since I'm running Tiger on my MacBook (10.4), I cannot upgrade to iTunes 10. Now I'm not even able to get to the store to buy songs. Am I completely out of luck here? Am I forced to upgrade my OS so that I can buy more iTunes songs? Or is there a way around this? I really don't want to spend extra money upgrading my OS.

Any help is obviously appreciated!