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 $22.68   5.593%   $23.9485   $23.95   $23.95   $23.90  
  Purchase #2 $176.58   13.451%   $200.3318   $200.33   $200.35   $200.30  
  Purchase #3 $66.93   4.697%   $70.0737   $70.07   $70.05   $70.10  
  Purchase #4 $183.41   6.474%   $195.284   $195.28   $195.30   $195.30  
  Purchase #5 $123.42   7.539%   $132.7246   $132.72   $132.70   $132.70  
  Purchase #6 $152.58   8.863%   $166.1032   $166.10   $166.10   $166.10  
  Purchase #7 $209.81   12.581%   $236.2062   $236.21   $236.20   $236.20  
  7 purchase totals = $935.41       $1,024.6720   $1,024.66   $1,024.65   $1,024.60