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 $233.93   5.865%   $247.65   $247.65   $247.65   $247.70  
  Purchase #2 $112.88   4.542%   $118.007   $118.01   $118.00   $118.00  
  Purchase #3 $72.92   12.300%   $81.8892   $81.89   $81.90   $81.90  
  Purchase #4 $89.50   5.617%   $94.5272   $94.53   $94.55   $94.50  
  Purchase #5 $223.78   4.563%   $233.9911   $233.99   $234.00   $234.00  
  Purchase #6 $100.71   13.848%   $114.6563   $114.66   $114.65   $114.70  
  Purchase #7 $138.32   3.310%   $142.8984   $142.90   $142.90   $142.90  
  7 purchase totals = $972.04       $1,033.6192   $1,033.63   $1,033.65   $1,033.70