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 $164.51   5.405%   $173.4018   $173.40   $173.40   $173.40  
  Purchase #2 $192.43   13.133%   $217.7018   $217.70   $217.70   $217.70  
  Purchase #3 $44.38   7.866%   $47.8709   $47.87   $47.85   $47.90  
  Purchase #4 $73.50   12.820%   $82.9227   $82.92   $82.90   $82.90  
  Purchase #5 $222.81   5.197%   $234.3894   $234.39   $234.40   $234.40  
  Purchase #6 $92.43   5.484%   $97.4989   $97.50   $97.50   $97.50  
  Purchase #7 $204.36   5.425%   $215.4465   $215.45   $215.45   $215.40  
  7 purchase totals = $994.42       $1,069.2320   $1,069.23   $1,069.20   $1,069.20