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 $195.99   8.483%   $212.6158   $212.62   $212.60   $212.60  
  Purchase #2 $103.94   9.852%   $114.1802   $114.18   $114.20   $114.20  
  Purchase #3 $165.80   7.521%   $178.2698   $178.27   $178.25   $178.30  
  Purchase #4 $230.53   3.157%   $237.8078   $237.81   $237.80   $237.80  
  Purchase #5 $13.78   12.610%   $15.5177   $15.52   $15.50   $15.50  
  Purchase #6 $58.53   3.126%   $60.3596   $60.36   $60.35   $60.40  
  Purchase #7 $248.50   5.232%   $261.5015   $261.50   $261.50   $261.50  
  7 purchase totals = $1,017.07       $1,080.2524   $1,080.26   $1,080.20   $1,080.30