ACCESS 2003 not recognizing two numbers as equal on a form

I have a form that the users inputs totals, then in another section they input details.  There is a check that the total amount should equal the sum of the details.  Most of the time it work,s but everynow and then (like now!) while the numers look the same, internally they are slighly different, so the VBA will throw an error and the user gets a message box his numbers don't match, when visually they do.  What would be the best approach to tell ACCESS that these numbers really are the same?  Right now I have 67,637.60 in two fields, but internally they have a slight difference.