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 $59.41   10.467%   $65.6284   $65.63   $65.65   $65.60  
  Purchase #2 $136.66   3.626%   $141.6153   $141.62   $141.60   $141.60  
  Purchase #3 $57.55   9.431%   $62.9775   $62.98   $63.00   $63.00  
  Purchase #4 $208.66   13.340%   $236.4952   $236.50   $236.50   $236.50  
  Purchase #5 $241.42   7.373%   $259.2199   $259.22   $259.20   $259.20  
  Purchase #6 $21.61   8.551%   $23.4579   $23.46   $23.45   $23.50  
  Purchase #7 $241.90   6.483%   $257.5824   $257.58   $257.60   $257.60  
  7 purchase totals = $967.21       $1,046.9766   $1,046.99   $1,047.00   $1,047.00