TORONTO - Canada's main stock index managed to eke out a minor gain Tuesday as U.S. stocks closed sharply higher after another volatile day. The Toronto stock Exchange's S&P/TSX composite index was ahead 29.12 points or 0.19 per cent at 15,363.93, led by strong gains in the health-care and base metals sectors. Trading was choppy in the early going Tuesday, after the TSX plunged in initial trading before paring its losses to 61.64 points or 0.4 ...