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 $176.57   4.382%   $184.3073   $184.31   $184.30   $184.30  
  Purchase #2 $248.33   7.738%   $267.5458   $267.55   $267.55   $267.50  
  Purchase #3 $74.78   3.476%   $77.3794   $77.38   $77.40   $77.40  
  Purchase #4 $119.44   10.857%   $132.4076   $132.41   $132.40   $132.40  
  Purchase #5 $192.90   8.293%   $208.8972   $208.90   $208.90   $208.90  
  Purchase #6 $231.82   5.601%   $244.8042   $244.80   $244.80   $244.80  
  Purchase #7 $74.26   3.308%   $76.7165   $76.72   $76.70   $76.70  
  7 purchase totals = $1,118.10       $1,192.0580   $1,192.07   $1,192.05   $1,192.00