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 $107.65   10.873%   $119.3548   $119.35   $119.35   $119.40  
  Purchase #2 $183.38   13.172%   $207.5348   $207.53   $207.55   $207.50  
  Purchase #3 $95.93   7.131%   $102.7708   $102.77   $102.75   $102.80  
  Purchase #4 $116.62   4.630%   $122.0195   $122.02   $122.00   $122.00  
  Purchase #5 $242.84   8.852%   $264.3362   $264.34   $264.35   $264.30  
  Purchase #6 $24.83   8.501%   $26.9408   $26.94   $26.95   $26.90  
  Purchase #7 $243.89   7.327%   $261.7598   $261.76   $261.75   $261.80  
  7 purchase totals = $1,015.14       $1,104.7167   $1,104.71   $1,104.70   $1,104.70