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 $214.38   4.770%   $224.6059   $224.61   $224.60   $224.60  
  Purchase #2 $41.62   6.383%   $44.2766   $44.28   $44.30   $44.30  
  Purchase #3 $27.58   5.571%   $29.1165   $29.12   $29.10   $29.10  
  Purchase #4 $60.27   10.699%   $66.7183   $66.72   $66.70   $66.70  
  Purchase #5 $163.84   4.408%   $171.0621   $171.06   $171.05   $171.10  
  Purchase #6 $59.81   12.231%   $67.1254   $67.13   $67.15   $67.10  
  Purchase #7 $170.43   7.506%   $183.2225   $183.22   $183.20   $183.20  
  7 purchase totals = $737.93       $786.1273   $786.14   $786.10   $786.10