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 $174.56   4.599%   $182.588   $182.59   $182.60   $182.60  
  Purchase #2 $237.33   10.645%   $262.5938   $262.59   $262.60   $262.60  
  Purchase #3 $188.81   3.536%   $195.4863   $195.49   $195.50   $195.50  
  Purchase #4 $119.73   8.144%   $129.4808   $129.48   $129.50   $129.50  
  Purchase #5 $94.36   10.857%   $104.6047   $104.60   $104.60   $104.60  
  Purchase #6 $240.50   11.610%   $268.4221   $268.42   $268.40   $268.40  
  Purchase #7 $114.57   8.600%   $124.423   $124.42   $124.40   $124.40  
  7 purchase totals = $1,169.86       $1,267.5987   $1,267.59   $1,267.60   $1,267.60