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 $161.51   7.537%   $173.683   $173.68   $173.70   $173.70  
  Purchase #2 $119.75   4.473%   $125.1064   $125.11   $125.10   $125.10  
  Purchase #3 $108.67   5.372%   $114.5078   $114.51   $114.50   $114.50  
  Purchase #4 $5.54   9.476%   $6.065   $6.07   $6.05   $6.10  
  Purchase #5 $171.27   3.581%   $177.4032   $177.40   $177.40   $177.40  
  Purchase #6 $48.87   10.397%   $53.951   $53.95   $53.95   $54.00  
  Purchase #7 $109.44   7.130%   $117.2431   $117.24   $117.25   $117.20  
  7 purchase totals = $725.05       $767.9595   $767.96   $767.95   $768.00