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 $55.95   11.217%   $62.2259   $62.23   $62.25   $62.20  
  Purchase #2 $181.26   11.319%   $201.7768   $201.78   $201.80   $201.80  
  Purchase #3 $175.75   5.354%   $185.1597   $185.16   $185.15   $185.20  
  Purchase #4 $237.80   10.339%   $262.3861   $262.39   $262.40   $262.40  
  Purchase #5 $196.99   3.193%   $203.2799   $203.28   $203.30   $203.30  
  Purchase #6 $185.49   5.276%   $195.2765   $195.28   $195.30   $195.30  
  Purchase #7 $52.48   5.746%   $55.4955   $55.50   $55.50   $55.50  
  7 purchase totals = $1,085.72       $1,165.6004   $1,165.62   $1,165.70   $1,165.70