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 $102.72   11.528%   $114.5616   $114.56   $114.55   $114.60  
  Purchase #2 $230.91   11.428%   $257.2984   $257.30   $257.30   $257.30  
  Purchase #3 $244.49   4.560%   $255.6387   $255.64   $255.65   $255.60  
  Purchase #4 $205.56   4.289%   $214.3765   $214.38   $214.40   $214.40  
  Purchase #5 $112.91   10.745%   $125.0422   $125.04   $125.05   $125.00  
  Purchase #6 $238.46   11.585%   $266.0856   $266.09   $266.10   $266.10  
  Purchase #7 $188.63   7.382%   $202.5547   $202.55   $202.55   $202.60  
  7 purchase totals = $1,323.68       $1,435.5577   $1,435.56   $1,435.60   $1,435.60