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 $147.76   9.630%   $161.9893   $161.99   $162.00   $162.00  
  Purchase #2 $84.97   11.162%   $94.4544   $94.45   $94.45   $94.50  
  Purchase #3 $22.34   4.737%   $23.3982   $23.40   $23.40   $23.40  
  Purchase #4 $218.61   7.402%   $234.7915   $234.79   $234.80   $234.80  
  Purchase #5 $235.83   11.620%   $263.2334   $263.23   $263.25   $263.20  
  Purchase #6 $241.62   8.632%   $262.4766   $262.48   $262.50   $262.50  
  Purchase #7 $82.46   12.302%   $92.6042   $92.60   $92.60   $92.60  
  7 purchase totals = $1,033.59       $1,132.9476   $1,132.94   $1,133.00   $1,133.00