The dollar edged down on Monday as renewed selling on oil markets drove investors into currencies often deemed less risky investments.
The dollar firmed Friday, boosted by expectations of monetary easing by in Europe and Japan, and by strong U.S. housing data.
The dollar turned negative against the euro on Thursday, reversing a morning rally.
The dollar fell to a more than one-year low against the Japanese yen as crude oil prices dropped near 13-year lows.
The dollar posted modest gains on Tuesday, as investor risk appetite improved on the back of rising oil prices and the expectation of further stimulus in China.
A recovery in stock markets helped the dollar gain ground against Europe's current safe havens of choice, the euro and the Swiss franc.
The dollar tumbled to a near five-month low against the yen and a 2-1/2-week trough versus the euro on Friday.
James Watson, MD for UK and Europe at ADS Securities, discusses the impact of last year's decision by the Swiss Nation Bank to remove the Swiss franc's peg with the euro.
The dollar rose on Thursday, bolstered by gains in the U.S. stock market and a rebound in oil prices.
The euro regained its footing against the U.S. dollar as risk appetite soured anew late in the afternoon.
The dollar rose for a third straight session as gains on Wall Street and calmer financial markets enhanced risk appetite.
The low-yielding euro fell for a second session, as steadier global stock markets prompted investors to seek other currencies.
The dollar climbed Friday on measures taken by China to ease this week's market turmoil and a hefty rise in U.S. jobs in December.
It hit a one-month low of $1.0709 two days ago.
The dollar weakened against a basket of currencies on Wednesday after the release of the FOMC minutes from its December meeting.
The yen rose on Tuesday as traders sought safety in the low-risk currency on anxiety about sluggish global growth.
The Japanese yen rose broadly, as financial market turbulence sent traders scrambling for the traditional low-risk currency.
The dollar ended 2015 with a more than 9 percent annual gain against a basket of currencies on Thursday.
The U.S. dollar rallied against commodity currencies such as the Norwegian crown and Russian ruble on Wednesday.
The U.S. dollar gained against the euro on Tuesday after greater risk appetite hurt demand for the shared currency.