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 $112.59   5.102%   $118.3343   $118.33   $118.35   $118.30  
  Purchase #2 $101.66   11.845%   $113.7016   $113.70   $113.70   $113.70  
  Purchase #3 $164.78   10.432%   $181.9698   $181.97   $181.95   $182.00  
  Purchase #4 $208.68   4.443%   $217.9517   $217.95   $217.95   $218.00  
  Purchase #5 $192.87   4.295%   $201.1538   $201.15   $201.15   $201.20  
  Purchase #6 $209.52   3.138%   $216.0947   $216.09   $216.10   $216.10  
  Purchase #7 $21.27   11.163%   $23.6444   $23.64   $23.65   $23.60  
  7 purchase totals = $1,011.37       $1,072.8503   $1,072.83   $1,072.85   $1,072.90