Does Procare auto-correct Social Security & Medicare withholdings?

Yes, but it depends on how recently you downloaded tax formulas.

Social Security:
Beginning with version 10.2.4393 (and tax formulas downloaded on or after 01/01/2012) withholdings for Social Security are automatically corrected if too much or too little was withheld on prior checks during the year. This means the amount withheld will not always be an exact percentage, like 4.2 or 6.2%.

Medicare:
Beginning with tax formulas downloaded on or after 9/18/2012 withholdings for Medicare are also automatically corrected if too much or too little was withheld. This means the amount withheld will not always be an exact percentage, like 1.45%.See also: How do I download the latest tax tables?