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 $201.55   7.271%   $216.2047   $216.20   $216.20   $216.20  
  Purchase #2 $195.92   5.532%   $206.7583   $206.76   $206.75   $206.80  
  Purchase #3 $85.38   7.351%   $91.6563   $91.66   $91.65   $91.70  
  Purchase #4 $208.76   11.841%   $233.4793   $233.48   $233.50   $233.50  
  Purchase #5 $175.57   5.158%   $184.6259   $184.63   $184.65   $184.60  
  Purchase #6 $143.55   5.691%   $151.7194   $151.72   $151.70   $151.70  
  Purchase #7 $68.86   8.531%   $74.7344   $74.73   $74.75   $74.70  
  7 purchase totals = $1,079.59       $1,159.1783   $1,159.18   $1,159.20   $1,159.20