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 $249.90   7.242%   $267.9978   $268.00   $268.00   $268.00  
  Purchase #2 $169.82   9.116%   $185.3008   $185.30   $185.30   $185.30  
  Purchase #3 $202.54   9.603%   $221.9899   $221.99   $222.00   $222.00  
  Purchase #4 $163.59   11.813%   $182.9149   $182.91   $182.90   $182.90  
  Purchase #5 $220.25   4.394%   $229.9278   $229.93   $229.95   $229.90  
  Purchase #6 $214.56   5.505%   $226.3715   $226.37   $226.35   $226.40  
  Purchase #7 $41.86   13.871%   $47.6664   $47.67   $47.65   $47.70  
  7 purchase totals = $1,262.52       $1,362.1691   $1,362.17   $1,362.15   $1,362.20