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 $61.66   9.281%   $67.3827   $67.38   $67.40   $67.40  
  Purchase #2 $161.64   7.208%   $173.291   $173.29   $173.30   $173.30  
  Purchase #3 $185.55   5.734%   $196.1894   $196.19   $196.20   $196.20  
  Purchase #4 $57.80   12.804%   $65.2007   $65.20   $65.20   $65.20  
  Purchase #5 $233.93   11.733%   $261.377   $261.38   $261.40   $261.40  
  Purchase #6 $149.44   10.328%   $164.8742   $164.87   $164.85   $164.90  
  Purchase #7 $189.77   9.531%   $207.857   $207.86   $207.85   $207.90  
  7 purchase totals = $1,039.79       $1,136.1720   $1,136.17   $1,136.20   $1,136.30