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 $93.95   8.158%   $101.6144   $101.61   $101.60   $101.60  
  Purchase #2 $32.45   8.340%   $35.1563   $35.16   $35.15   $35.20  
  Purchase #3 $125.79   8.352%   $136.296   $136.30   $136.30   $136.30  
  Purchase #4 $39.67   9.201%   $43.32   $43.32   $43.30   $43.30  
  Purchase #5 $21.93   12.296%   $24.6265   $24.63   $24.65   $24.60  
  Purchase #6 $192.34   11.676%   $214.7976   $214.80   $214.80   $214.80  
  Purchase #7 $51.95   13.553%   $58.9908   $58.99   $59.00   $59.00  
  7 purchase totals = $558.08       $614.8016   $614.81   $614.80   $614.80