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 $86.98   10.316%   $95.9529   $95.95   $95.95   $96.00  
  Purchase #2 $34.63   13.395%   $39.2687   $39.27   $39.25   $39.30  
  Purchase #3 $21.38   9.152%   $23.3367   $23.34   $23.35   $23.30  
  Purchase #4 $184.76   5.849%   $195.5666   $195.57   $195.55   $195.60  
  Purchase #5 $195.88   9.668%   $214.8177   $214.82   $214.80   $214.80  
  Purchase #6 $25.63   13.755%   $29.1554   $29.16   $29.15   $29.20  
  Purchase #7 $42.45   9.397%   $46.439   $46.44   $46.45   $46.40  
  7 purchase totals = $591.71       $644.5370   $644.55   $644.50   $644.60