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 $116.89   5.743%   $123.603   $123.60   $123.60   $123.60  
  Purchase #2 $119.79   4.638%   $125.3459   $125.35   $125.35   $125.30  
  Purchase #3 $121.49   4.309%   $126.725   $126.73   $126.75   $126.70  
  Purchase #4 $69.83   10.632%   $77.2543   $77.25   $77.25   $77.30  
  Purchase #5 $56.32   6.501%   $59.9814   $59.98   $60.00   $60.00  
  Purchase #6 $170.77   3.703%   $177.0936   $177.09   $177.10   $177.10  
  Purchase #7 $208.59   8.335%   $225.976   $225.98   $226.00   $226.00  
  7 purchase totals = $863.68       $915.9792   $915.98   $916.05   $916.00