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 $114.44   10.236%   $126.1541   $126.15   $126.15   $126.20  
  Purchase #2 $214.51   10.619%   $237.2888   $237.29   $237.30   $237.30  
  Purchase #3 $157.41   8.204%   $170.3239   $170.32   $170.30   $170.30  
  Purchase #4 $109.73   9.385%   $120.0282   $120.03   $120.05   $120.00  
  Purchase #5 $110.84   5.667%   $117.1213   $117.12   $117.10   $117.10  
  Purchase #6 $199.26   12.531%   $224.2293   $224.23   $224.25   $224.20  
  Purchase #7 $58.89   13.128%   $66.6211   $66.62   $66.60   $66.60  
  7 purchase totals = $965.08       $1,061.7667   $1,061.76   $1,061.75   $1,061.70