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 $67.25   13.221%   $76.1411   $76.14   $76.15   $76.10  
  Purchase #2 $64.88   3.136%   $66.9146   $66.91   $66.90   $66.90  
  Purchase #3 $180.93   5.244%   $190.418   $190.42   $190.40   $190.40  
  Purchase #4 $185.85   4.833%   $194.8321   $194.83   $194.85   $194.80  
  Purchase #5 $159.68   10.754%   $176.852   $176.85   $176.85   $176.90  
  Purchase #6 $178.49   9.300%   $195.0896   $195.09   $195.10   $195.10  
  Purchase #7 $161.74   3.177%   $166.8785   $166.88   $166.90   $166.90  
  7 purchase totals = $998.82       $1,067.1259   $1,067.12   $1,067.15   $1,067.10