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 $245.25   6.826%   $261.9908   $261.99   $262.00   $262.00  
  Purchase #2 $250.67   6.259%   $266.3594   $266.36   $266.35   $266.40  
  Purchase #3 $133.31   11.146%   $148.1687   $148.17   $148.15   $148.20  
  Purchase #4 $219.94   7.461%   $236.3497   $236.35   $236.35   $236.30  
  Purchase #5 $127.97   6.251%   $135.9694   $135.97   $135.95   $136.00  
  Purchase #6 $248.56   7.638%   $267.545   $267.55   $267.55   $267.50  
  Purchase #7 $220.25   5.163%   $231.6215   $231.62   $231.60   $231.60  
  7 purchase totals = $1,445.95       $1,548.0045   $1,548.01   $1,547.95   $1,548.00