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 $172.96   5.652%   $182.7357   $182.74   $182.75   $182.70  
  Purchase #2 $45.30   10.806%   $50.1951   $50.20   $50.20   $50.20  
  Purchase #3 $249.55   10.669%   $276.1745   $276.17   $276.15   $276.20  
  Purchase #4 $32.84   6.584%   $35.0022   $35.00   $35.00   $35.00  
  Purchase #5 $122.38   8.630%   $132.9414   $132.94   $132.95   $132.90  
  Purchase #6 $232.90   10.786%   $258.0206   $258.02   $258.00   $258.00  
  Purchase #7 $211.63   9.611%   $231.9698   $231.97   $231.95   $232.00  
  7 purchase totals = $1,067.56       $1,167.0393   $1,167.04   $1,167.00   $1,167.00