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 $66.25   11.134%   $73.6263   $73.63   $73.65   $73.60  
  Purchase #2 $158.88   9.685%   $174.2675   $174.27   $174.25   $174.30  
  Purchase #3 $173.84   12.530%   $195.6222   $195.62   $195.60   $195.60  
  Purchase #4 $55.42   9.243%   $60.5425   $60.54   $60.55   $60.50  
  Purchase #5 $63.95   10.372%   $70.5829   $70.58   $70.60   $70.60  
  Purchase #6 $177.71   10.345%   $196.0941   $196.09   $196.10   $196.10  
  Purchase #7 $26.61   13.804%   $30.2832   $30.28   $30.30   $30.30  
  7 purchase totals = $722.66       $801.0187   $801.01   $801.05   $801.00