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 $119.90   5.402%   $126.377   $126.38   $126.40   $126.40  
  Purchase #2 $186.62   4.324%   $194.6894   $194.69   $194.70   $194.70  
  Purchase #3 $203.71   7.799%   $219.5973   $219.60   $219.60   $219.60  
  Purchase #4 $191.99   12.703%   $216.3785   $216.38   $216.40   $216.40  
  Purchase #5 $193.42   6.612%   $206.2089   $206.21   $206.20   $206.20  
  Purchase #6 $158.94   5.531%   $167.731   $167.73   $167.75   $167.70  
  Purchase #7 $213.51   11.181%   $237.3826   $237.38   $237.40   $237.40  
  7 purchase totals = $1,268.09       $1,368.3647   $1,368.37   $1,368.45   $1,368.40