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 $90.98   4.307%   $94.8985   $94.90   $94.90   $94.90  
  Purchase #2 $162.74   10.792%   $180.3029   $180.30   $180.30   $180.30  
  Purchase #3 $44.57   11.394%   $49.6483   $49.65   $49.65   $49.60  
  Purchase #4 $138.86   7.136%   $148.769   $148.77   $148.75   $148.80  
  Purchase #5 $248.43   5.165%   $261.2614   $261.26   $261.25   $261.30  
  Purchase #6 $107.74   11.135%   $119.7368   $119.74   $119.75   $119.70  
  Purchase #7 $166.54   3.199%   $171.8676   $171.87   $171.85   $171.90  
  7 purchase totals = $959.86       $1,026.4845   $1,026.49   $1,026.45   $1,026.50