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 $56.79   10.218%   $62.5928   $62.59   $62.60   $62.60  
  Purchase #2 $184.99   12.235%   $207.6235   $207.62   $207.60   $207.60  
  Purchase #3 $180.27   10.770%   $199.6851   $199.69   $199.70   $199.70  
  Purchase #4 $59.66   3.465%   $61.7272   $61.73   $61.75   $61.70  
  Purchase #5 $55.39   13.661%   $62.9568   $62.96   $62.95   $63.00  
  Purchase #6 $125.47   11.166%   $139.48   $139.48   $139.50   $139.50  
  Purchase #7 $239.64   8.836%   $260.8146   $260.81   $260.80   $260.80  
  7 purchase totals = $902.21       $994.8800   $994.88   $994.90   $994.90