First off, it's so cool that Jesus tells Peter to go fishing, catch a fish, dig into it's mouth, pull out a coin, and use that to pay for the temple tax.
I wonder why Jesus paid. I mean, I wonder why he said that he didn't want to upset the tax collectors. He didn't seem to mind upsetting other people who were following religious rules. I think it's because he didn't see the need to embarrass Peter. Peter had already been put on the spot and told the tax collectors that Jesus would pay the tax. I don't really think it would benefit Jesus to tell Peter that he doesn't pay it and to send Peter back out to say No, he doesn't pay it, so what's it to ya?