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 $88.43   4.660%   $92.5508   $92.55   $92.55   $92.60  
  Purchase #2 $249.91   5.621%   $263.9574   $263.96   $263.95   $264.00  
  Purchase #3 $184.39   13.434%   $209.161   $209.16   $209.15   $209.20  
  Purchase #4 $220.46   12.548%   $248.1233   $248.12   $248.10   $248.10  
  Purchase #5 $57.86   10.840%   $64.132   $64.13   $64.15   $64.10  
  Purchase #6 $240.92   8.549%   $261.5163   $261.52   $261.50   $261.50  
  Purchase #7 $212.48   12.726%   $239.5202   $239.52   $239.50   $239.50  
  7 purchase totals = $1,254.45       $1,378.9610   $1,378.96   $1,378.90   $1,379.00