The safe-haven yen rose as investor risk aversion mounted following a sharp drop in crude oil and stocks.
The euro fell to near a nine-year low, hit by concerns that Greek elections will result in a government that will aim to cancel austerity measures.
The euro fell to its lowest in 4-1/2 years against the dollar on Friday after the head of the ECB fanned expectations of QE later this month.
The U.S. dollar hit its highest level since March 2006 on Friday, as the euro fell on speculation about imminent monetary easing tactics.
The dollar was set to end 2014 with a gain of more than 12 percent against a basket of major currencies on Wednesday.
The yen gained sharply against both the dollar and euro on Tuesday as investors sought the traditional safety of the Japanese currency.
The euro inched up but remained near two-year-lows after a key vote in Greece failed to secure a new president.
The dollar edged up against the yen on Friday on light bargain hunting, with markets slowly getting into gear after the Christmas holiday.
Currency strategists are pondering whether there is more volatility in store for the ruble.
The dollar hovered at its highest in nearly nine years after strong U.S. economic growth caused market speculation of earlier interest rate hike.
The euro bounced back from two-year lows against a slightly weaker dollar on Monday, with Greece's election among risks to a calmer mood.
The U.S. dollar rose against major currencies for a third session on diverging monetary policy between the Federal Reserve and other central banks.
The dollar pared gains against major currencies on Wednesday after the Fed said there remains "considerable time" before an interest rate hike.
The U.S. dollar slipped against major currencies on Tuesday on expectations that the Federal Reserve would take a cautious tone.
Emergency measures by the Russian central bank Monday night looked to have fallen short within hours of their announcement.
The U.S. dollar rose against the euro on Monday on expectations that the Federal Reserve will take a less-dovish stance on monetary policy.
The Norwegian crown sank to its weakest in more than a decade against the U.S. dollar on Friday, a day after Norway's central bank cut rates.
The dollar was boosted by strong U.S. retail sales numbers and declining jobless claims, suggesting the US economy may get a rate hike next year.
Kathy Lien, BK Asset Management; Richard Mallinson, Energy Aspects, and Scott Nations, NationShares, discuss oil's decline, global currencies, and the markets.
The euro edged higher against the dollar, but investors remained nervous over an uncertain political situation in Greece.