WHEN CONGRESS passed a $350 billion tax bill last year, lawmakers managed to cram the measure into that preset spending ceiling by scheduling the most popular tax breaks to expire at the end of this year. That gimmick made the cost of the 10-year bill look lower, though no one believed that the cuts would be allowed to evaporate. And, of course, they won't. The House has already approved extensions, and the Senate is expected to take up the issue next week.