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 $47.29   4.422%   $49.3812   $49.38   $49.40   $49.40  
  Purchase #2 $195.63   10.530%   $216.2298   $216.23   $216.25   $216.20  
  Purchase #3 $224.78   4.105%   $234.0072   $234.01   $234.00   $234.00  
  Purchase #4 $213.39   5.733%   $225.6236   $225.62   $225.60   $225.60  
  Purchase #5 $219.29   6.239%   $232.9715   $232.97   $232.95   $233.00  
  Purchase #6 $245.99   6.291%   $261.4652   $261.47   $261.45   $261.50  
  Purchase #7 $148.91   3.615%   $154.2931   $154.29   $154.30   $154.30  
  7 purchase totals = $1,295.28       $1,373.9716   $1,373.97   $1,373.95   $1,374.00