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 $58.75   7.569%   $63.1968   $63.20   $63.20   $63.20  
  Purchase #2 $244.76   3.199%   $252.5899   $252.59   $252.60   $252.60  
  Purchase #3 $19.98   13.210%   $22.6194   $22.62   $22.60   $22.60  
  Purchase #4 $229.34   9.266%   $250.5906   $250.59   $250.60   $250.60  
  Purchase #5 $127.69   9.308%   $139.5754   $139.58   $139.60   $139.60  
  Purchase #6 $9.78   3.728%   $10.1446   $10.14   $10.15   $10.10  
  Purchase #7 $103.49   10.105%   $113.9477   $113.95   $113.95   $113.90  
  7 purchase totals = $793.79       $852.6644   $852.67   $852.70   $852.60