The IRS has a friendly message on its website reminding you to report all amounts on your tax return in USD, not yen. And they even have helpful links at the bottom of the page to the Federal Reserve Bank and Treasury Department websites. But those links just take you to the top of each respective site, which doesn't help me much: Every year as I search for the annual rates on the FRB website, I inevitably get lost in the pages and pages of other rates: daily, weekly, and monthly.
You'd think the IRS would link straight to the annual stuff, since that's probably what most people landing on the redirect page are looking for. But anyway, this year I'm setting myself straight and posting direct links for myself for next year. I hope it can be of use to some other lost souls:
Annual Foreign Exchange Rates from the Federal Reserve Bank
(in FRB lingo, this is Release G5.A)
U.S. Tax Information from the American Embassy in Tokyo, Japan
(includes a simple chart with annual JPY exchange rates for the last four years)