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 $242.75   7.655%   $261.3325   $261.33   $261.35   $261.30  
  Purchase #2 $116.48   6.820%   $124.4239   $124.42   $124.40   $124.40  
  Purchase #3 $95.95   11.757%   $107.2308   $107.23   $107.25   $107.20  
  Purchase #4 $208.76   10.856%   $231.423   $231.42   $231.40   $231.40  
  Purchase #5 $202.25   10.180%   $222.8391   $222.84   $222.85   $222.80  
  Purchase #6 $198.59   11.315%   $221.0605   $221.06   $221.05   $221.10  
  Purchase #7 $41.77   11.605%   $46.6174   $46.62   $46.60   $46.60  
  7 purchase totals = $1,106.55       $1,214.9272   $1,214.92   $1,214.90   $1,214.80