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 $93.86   4.674%   $98.247   $98.25   $98.25   $98.20  
  Purchase #2 $109.64   7.603%   $117.9759   $117.98   $118.00   $118.00  
  Purchase #3 $146.73   13.469%   $166.4931   $166.49   $166.50   $166.50  
  Purchase #4 $172.62   5.586%   $182.2626   $182.26   $182.25   $182.30  
  Purchase #5 $114.78   10.583%   $126.9272   $126.93   $126.95   $126.90  
  Purchase #6 $162.82   11.157%   $180.9858   $180.99   $181.00   $181.00  
  Purchase #7 $160.66   13.389%   $182.1708   $182.17   $182.15   $182.20  
  7 purchase totals = $961.11       $1,055.0624   $1,055.07   $1,055.10   $1,055.10