Retail inflation based on the consumer price index (CPI) rose to a nine-month high of 5.5% in Sept (y-o-y) from 4.8% in Aug, on account of a surge in food prices, which strained household costs, National Statistics Office data released Monday showed. This was the first time that retail inflation crossed the 5% mark under the new CPI series, which was released earlier this year, remaining above the Reserve Bank of India's (RBI) 4% target for the fourth consecutive month, although the headline figure still remains within the central bank's tolerance band of 2-6%.