Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $46.29   3.787%   $48.043   $48.04   $48.05   $48.00  
  Purchase #2 $66.62   13.283%   $75.4691   $75.47   $75.45   $75.50  
  Purchase #3 $89.90   13.307%   $101.863   $101.86   $101.85   $101.90  
  Purchase #4 $240.80   8.489%   $261.2415   $261.24   $261.25   $261.20  
  Purchase #5 $212.63   11.341%   $236.7444   $236.74   $236.75   $236.70  
  Purchase #6 $68.80   5.103%   $72.3109   $72.31   $72.30   $72.30  
  Purchase #7 $196.97   10.515%   $217.6814   $217.68   $217.70   $217.70  
  7 purchase totals = $922.01       $1,013.3533   $1,013.34   $1,013.35   $1,013.30