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 $167.25   5.606%   $176.626   $176.63   $176.65   $176.60  
  Purchase #2 $90.38   8.342%   $97.9195   $97.92   $97.90   $97.90  
  Purchase #3 $162.48   6.706%   $173.3759   $173.38   $173.40   $173.40  
  Purchase #4 $122.74   9.725%   $134.6765   $134.68   $134.70   $134.70  
  Purchase #5 $130.48   10.407%   $144.0591   $144.06   $144.05   $144.10  
  Purchase #6 $77.30   9.108%   $84.3405   $84.34   $84.35   $84.30  
  Purchase #7 $12.44   7.351%   $13.3545   $13.35   $13.35   $13.40  
  7 purchase totals = $763.07       $824.3520   $824.36   $824.40   $824.40