If the market is truly worried about a Greek debt default, it wasn’t apparent Tuesday as stocks ended with decent gains in lower volume. The Dow and S&P 500 each rose 0.6%. The Nasdaq gained 0.5%. The IBD 50 lagged a bit, rising 0.4%. The IBD 50 closed above its 50-day moving average for the 15th straight session. Nasdaq volume fell 5% from Monday’s level. NYSE volume fell 4%.