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   6.737%   $62.708   $62.71   $62.70   $62.70  
  Purchase #2 $113.83   10.345%   $125.6057   $125.61   $125.60   $125.60  
  Purchase #3 $137.87   12.808%   $155.5284   $155.53   $155.55   $155.50  
  Purchase #4 $164.45   5.144%   $172.9093   $172.91   $172.90   $172.90  
  Purchase #5 $43.63   4.161%   $45.4454   $45.45   $45.45   $45.40  
  Purchase #6 $146.48   11.352%   $163.1084   $163.11   $163.10   $163.10  
  Purchase #7 $136.55   4.808%   $143.1153   $143.12   $143.10   $143.10  
  7 purchase totals = $801.56       $868.4205   $868.44   $868.40   $868.30