Sentence:  <WSD>Round off</WSD> 15.4 to 15, <WSD>round off</WSD> 15.51 to 15.5 or to 16, <WSD>round off</WSD> 0.499 to 0, and <WSD>round off</WSD> 970,000 to 1 million. 
Meaning of the word marked with <WSD> tags:  To change a number into an approximation having fewer significant digits.