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 $215.58   4.447%   $225.1668   $225.17   $225.15   $225.20  
  Purchase #2 $83.41   12.528%   $93.8596   $93.86   $93.85   $93.90  
  Purchase #3 $133.87   6.354%   $142.3761   $142.38   $142.40   $142.40  
  Purchase #4 $193.35   8.449%   $209.6861   $209.69   $209.70   $209.70  
  Purchase #5 $218.67   13.246%   $247.635   $247.64   $247.65   $247.60  
  Purchase #6 $249.30   4.854%   $261.401   $261.40   $261.40   $261.40  
  Purchase #7 $14.64   4.517%   $15.3013   $15.30   $15.30   $15.30  
  7 purchase totals = $1,108.82       $1,195.4259   $1,195.44   $1,195.45   $1,195.50