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 $244.88   7.391%   $262.9791   $262.98   $263.00   $263.00  
  Purchase #2 $109.52   4.681%   $114.6466   $114.65   $114.65   $114.60  
  Purchase #3 $131.75   7.670%   $141.8552   $141.86   $141.85   $141.90  
  Purchase #4 $235.86   3.187%   $243.3769   $243.38   $243.40   $243.40  
  Purchase #5 $56.66   6.349%   $60.2573   $60.26   $60.25   $60.30  
  Purchase #6 $234.50   11.679%   $261.8873   $261.89   $261.90   $261.90  
  Purchase #7 $108.99   10.233%   $120.1429   $120.14   $120.15   $120.10  
  7 purchase totals = $1,122.16       $1,205.1453   $1,205.16   $1,205.20   $1,205.20