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 $117.82   6.707%   $125.7222   $125.72   $125.70   $125.70  
  Purchase #2 $160.90   8.559%   $174.6714   $174.67   $174.65   $174.70  
  Purchase #3 $221.75   5.795%   $234.6004   $234.60   $234.60   $234.60  
  Purchase #4 $160.85   5.625%   $169.8978   $169.90   $169.90   $169.90  
  Purchase #5 $157.76   9.836%   $173.2773   $173.28   $173.30   $173.30  
  Purchase #6 $16.73   9.843%   $18.3767   $18.38   $18.40   $18.40  
  Purchase #7 $214.78   9.133%   $234.3959   $234.40   $234.40   $234.40  
  7 purchase totals = $1,050.59       $1,130.9417   $1,130.95   $1,130.95   $1,131.00