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 $173.99   13.412%   $197.3255   $197.33   $197.35   $197.30  
  Purchase #2 $65.96   10.440%   $72.8462   $72.85   $72.85   $72.80  
  Purchase #3 $24.97   4.843%   $26.1793   $26.18   $26.20   $26.20  
  Purchase #4 $93.36   13.204%   $105.6873   $105.69   $105.70   $105.70  
  Purchase #5 $158.76   5.302%   $167.1775   $167.18   $167.20   $167.20  
  Purchase #6 $54.39   4.232%   $56.6918   $56.69   $56.70   $56.70  
  Purchase #7 $247.71   5.550%   $261.4579   $261.46   $261.45   $261.50  
  7 purchase totals = $819.14       $887.3655   $887.38   $887.45   $887.40