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 $214.25   5.794%   $226.6636   $226.66   $226.65   $226.70  
  Purchase #2 $178.34   11.177%   $198.2731   $198.27   $198.25   $198.30  
  Purchase #3 $155.64   7.742%   $167.6896   $167.69   $167.70   $167.70  
  Purchase #4 $97.38   11.167%   $108.2544   $108.25   $108.25   $108.30  
  Purchase #5 $133.34   4.309%   $139.0856   $139.09   $139.10   $139.10  
  Purchase #6 $76.83   11.186%   $85.4242   $85.42   $85.40   $85.40  
  Purchase #7 $187.58   3.581%   $194.2972   $194.30   $194.30   $194.30  
  7 purchase totals = $1,043.36       $1,119.6877   $1,119.68   $1,119.65   $1,119.80