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 $57.71   8.632%   $62.6915   $62.69   $62.70   $62.70  
  Purchase #2 $242.73   6.783%   $259.1944   $259.19   $259.20   $259.20  
  Purchase #3 $76.25   11.650%   $85.1331   $85.13   $85.15   $85.10  
  Purchase #4 $23.89   9.243%   $26.0982   $26.10   $26.10   $26.10  
  Purchase #5 $25.89   8.123%   $27.993   $27.99   $28.00   $28.00  
  Purchase #6 $118.38   5.608%   $125.0188   $125.02   $125.00   $125.00  
  Purchase #7 $177.86   12.704%   $200.4553   $200.46   $200.45   $200.50  
  7 purchase totals = $722.71       $786.5843   $786.58   $786.60   $786.60