Tax-sheltered retirement plans offer the convenience of automatic investments and tax breaks-pretax contributions and tax-deferred compounding for traditional 401(k)s and tax-free compounding and withdrawals for Roth contributions. But the availability and quality of the 401(k) are also important considerations. Some workers don't have access to an employer-provided retirement plan, and 401(k) quality can be uneven. High administrative costs, meager employer matching contributions, and costly investment lineups can detract from 401(k)s' tax-saving features.