Canadian retail sales rose in May at the fastest rate in almost a decade, adding to pressure on the country’s central bank to keep raising interest rates. Sales rose 2.8 percent, to 35 billion Canadian dollars ($33.7 billion), Statistics Canada said. May’s increase was the fastest since December 1997, the statistics agency said. The retail sales report “pretty much cements the September rate hike and raises some questions about whether the bank might need to do more before the end of the year,” said Ted Carmichael, chief Canadian economist for JPMorgan Securities in Toronto.