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 $104.69   9.256%   $114.3801   $114.38   $114.40   $114.40  
  Purchase #2 $95.49   4.348%   $99.6419   $99.64   $99.65   $99.60  
  Purchase #3 $63.99   8.293%   $69.2967   $69.30   $69.30   $69.30  
  Purchase #4 $107.26   6.535%   $114.2694   $114.27   $114.25   $114.30  
  Purchase #5 $235.44   3.212%   $243.0023   $243.00   $243.00   $243.00  
  Purchase #6 $101.77   4.275%   $106.1207   $106.12   $106.10   $106.10  
  Purchase #7 $199.63   9.519%   $218.6328   $218.63   $218.65   $218.60  
  7 purchase totals = $908.27       $965.3439   $965.34   $965.35   $965.30