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 $94.47   13.214%   $106.9533   $106.95   $106.95   $107.00  
  Purchase #2 $103.83   9.357%   $113.5454   $113.55   $113.55   $113.50  
  Purchase #3 $152.85   9.522%   $167.4044   $167.40   $167.40   $167.40  
  Purchase #4 $217.43   3.551%   $225.1509   $225.15   $225.15   $225.20  
  Purchase #5 $214.34   6.158%   $227.5391   $227.54   $227.55   $227.50  
  Purchase #6 $48.55   8.475%   $52.6646   $52.66   $52.65   $52.70  
  Purchase #7 $38.63   5.428%   $40.7268   $40.73   $40.75   $40.70  
  7 purchase totals = $870.10       $933.9845   $933.98   $934.00   $934.00