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 $12.93   8.709%   $14.0561   $14.06   $14.05   $14.10  
  Purchase #2 $170.57   8.426%   $184.9422   $184.94   $184.95   $184.90  
  Purchase #3 $63.94   13.752%   $72.733   $72.73   $72.75   $72.70  
  Purchase #4 $223.70   8.423%   $242.5423   $242.54   $242.55   $242.50  
  Purchase #5 $44.60   12.668%   $50.2499   $50.25   $50.25   $50.20  
  Purchase #6 $152.83   5.691%   $161.5276   $161.53   $161.55   $161.50  
  Purchase #7 $35.98   4.438%   $37.5768   $37.58   $37.60   $37.60  
  7 purchase totals = $704.55       $763.6279   $763.63   $763.70   $763.50