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 $204.37   9.627%   $224.0447   $224.04   $224.05   $224.00  
  Purchase #2 $208.65   6.655%   $222.5357   $222.54   $222.55   $222.50  
  Purchase #3 $146.55   4.659%   $153.3778   $153.38   $153.40   $153.40  
  Purchase #4 $14.36   8.657%   $15.6031   $15.60   $15.60   $15.60  
  Purchase #5 $120.27   11.167%   $133.7006   $133.70   $133.70   $133.70  
  Purchase #6 $93.87   6.825%   $100.2766   $100.28   $100.30   $100.30  
  Purchase #7 $86.74   6.525%   $92.3998   $92.40   $92.40   $92.40  
  7 purchase totals = $874.81       $941.9383   $941.94   $942.00   $941.90