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 $33.27   4.274%   $34.692   $34.69   $34.70   $34.70  
  Purchase #2 $121.82   4.622%   $127.4505   $127.45   $127.45   $127.50  
  Purchase #3 $134.40   9.156%   $146.7057   $146.71   $146.70   $146.70  
  Purchase #4 $38.43   6.361%   $40.8745   $40.87   $40.85   $40.90  
  Purchase #5 $115.78   8.131%   $125.1941   $125.19   $125.20   $125.20  
  Purchase #6 $68.76   8.452%   $74.5716   $74.57   $74.55   $74.60  
  Purchase #7 $212.41   3.545%   $219.9399   $219.94   $219.95   $219.90  
  7 purchase totals = $724.87       $769.4283   $769.42   $769.40   $769.50