TORONTO, Aug 5 (Reuters) - Canada's main stock index fell on Tuesday as sluggish economic data from China and renewed geopolitical tensions in Ukraine weighed. The Toronto Stock Exchange's S&P/TSX composite index unofficially closed down 27.55 points, or 0.18 percent, and 15,187.71. Five of the 10 main sectors on the index were in the red. (Reporting by John Tilak; Editing by Meredith Mazzilli)