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 $232.45   12.710%   $261.9944   $261.99   $262.00   $262.00  
  Purchase #2 $187.33   7.623%   $201.6102   $201.61   $201.60   $201.60  
  Purchase #3 $129.83   10.109%   $142.9545   $142.95   $142.95   $143.00  
  Purchase #4 $90.35   3.609%   $93.6107   $93.61   $93.60   $93.60  
  Purchase #5 $105.52   8.268%   $114.2444   $114.24   $114.25   $114.20  
  Purchase #6 $24.45   4.696%   $25.5982   $25.60   $25.60   $25.60  
  Purchase #7 $176.60   5.655%   $186.5867   $186.59   $186.60   $186.60  
  7 purchase totals = $946.53       $1,026.5991   $1,026.59   $1,026.60   $1,026.60