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 $62.37   7.606%   $67.1139   $67.11   $67.10   $67.10  
  Purchase #2 $107.83   8.491%   $116.9858   $116.99   $117.00   $117.00  
  Purchase #3 $72.25   3.552%   $74.8163   $74.82   $74.80   $74.80  
  Purchase #4 $43.69   6.288%   $46.4372   $46.44   $46.45   $46.40  
  Purchase #5 $208.59   8.675%   $226.6852   $226.69   $226.70   $226.70  
  Purchase #6 $133.63   13.372%   $151.499   $151.50   $151.50   $151.50  
  Purchase #7 $242.82   4.620%   $254.0383   $254.04   $254.05   $254.00  
  7 purchase totals = $871.18       $937.5757   $937.59   $937.60   $937.50