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 $68.41   5.194%   $71.9632   $71.96   $71.95   $72.00  
  Purchase #2 $114.78   9.106%   $125.2319   $125.23   $125.25   $125.20  
  Purchase #3 $68.84   13.566%   $78.1788   $78.18   $78.20   $78.20  
  Purchase #4 $46.78   4.259%   $48.7724   $48.77   $48.75   $48.80  
  Purchase #5 $226.28   8.341%   $245.154   $245.15   $245.15   $245.20  
  Purchase #6 $148.65   9.723%   $163.1032   $163.10   $163.10   $163.10  
  Purchase #7 $213.89   13.607%   $242.994   $242.99   $243.00   $243.00  
  7 purchase totals = $887.63       $975.3975   $975.38   $975.40   $975.50