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 $40.25   7.333%   $43.2015   $43.20   $43.20   $43.20  
  Purchase #2 $125.28   8.710%   $136.1919   $136.19   $136.20   $136.20  
  Purchase #3 $212.95   5.617%   $224.9114   $224.91   $224.90   $224.90  
  Purchase #4 $151.87   3.141%   $156.6402   $156.64   $156.65   $156.60  
  Purchase #5 $170.55   11.105%   $189.4896   $189.49   $189.50   $189.50  
  Purchase #6 $195.38   3.376%   $201.976   $201.98   $202.00   $202.00  
  Purchase #7 $241.83   3.457%   $250.1901   $250.19   $250.20   $250.20  
  7 purchase totals = $1,138.11       $1,202.6007   $1,202.60   $1,202.65   $1,202.60