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 $107.46   5.619%   $113.4982   $113.50   $113.50   $113.50  
  Purchase #2 $40.88   11.110%   $45.4218   $45.42   $45.40   $45.40  
  Purchase #3 $150.57   6.649%   $160.5814   $160.58   $160.60   $160.60  
  Purchase #4 $96.62   7.401%   $103.7708   $103.77   $103.75   $103.80  
  Purchase #5 $24.67   3.593%   $25.5564   $25.56   $25.55   $25.60  
  Purchase #6 $94.51   3.797%   $98.0985   $98.10   $98.10   $98.10  
  Purchase #7 $195.91   6.672%   $208.9811   $208.98   $209.00   $209.00  
  7 purchase totals = $710.62       $755.9082   $755.91   $755.90   $756.00