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 $104.76   9.441%   $114.6504   $114.65   $114.65   $114.70  
  Purchase #2 $55.80   8.680%   $60.6434   $60.64   $60.65   $60.60  
  Purchase #3 $14.35   8.733%   $15.6032   $15.60   $15.60   $15.60  
  Purchase #4 $85.61   9.238%   $93.5187   $93.52   $93.50   $93.50  
  Purchase #5 $112.38   6.626%   $119.8263   $119.83   $119.85   $119.80  
  Purchase #6 $201.30   11.125%   $223.6946   $223.69   $223.70   $223.70  
  Purchase #7 $88.75   12.752%   $100.0674   $100.07   $100.05   $100.10  
  7 purchase totals = $662.95       $728.0040   $728.00   $728.00   $728.00