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 $121.76   3.200%   $125.6563   $125.66   $125.65   $125.70  
  Purchase #2 $157.99   4.648%   $165.3334   $165.33   $165.35   $165.30  
  Purchase #3 $61.53   3.333%   $63.5808   $63.58   $63.60   $63.60  
  Purchase #4 $217.60   5.779%   $230.1751   $230.18   $230.20   $230.20  
  Purchase #5 $117.69   3.198%   $121.4537   $121.45   $121.45   $121.50  
  Purchase #6 $125.89   11.142%   $139.9167   $139.92   $139.90   $139.90  
  Purchase #7 $162.83   3.486%   $168.5063   $168.51   $168.50   $168.50  
  7 purchase totals = $965.29       $1,014.6223   $1,014.63   $1,014.65   $1,014.70