OnClientClick and Postback

I created a small grid that looks like this:
Intuitively, it makes no sense for the "Discard" button at the bottom to be enabled if none of the checkboxes above it are selected.

After building the JavaScript to handle this logic, I thought I had done everything correctly. But I noticed that everytime I pressed the "Toggle" LinkButton, a postback was performed. Considering that I had no server-side code wired up for this control, I was most confused. I did a little research and discovered that when using the OnClientClick property, you need to explicitly return false or a postback will occur.