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 $183.46   7.520%   $197.2562   $197.26   $197.25   $197.30  
  Purchase #2 $164.93   3.605%   $170.8757   $170.88   $170.90   $170.90  
  Purchase #3 $238.63   8.855%   $259.7607   $259.76   $259.75   $259.80  
  Purchase #4 $41.91   13.554%   $47.5905   $47.59   $47.60   $47.60  
  Purchase #5 $104.60   8.403%   $113.3895   $113.39   $113.40   $113.40  
  Purchase #6 $136.54   6.189%   $144.9905   $144.99   $145.00   $145.00  
  Purchase #7 $141.56   13.776%   $161.0613   $161.06   $161.05   $161.10  
  7 purchase totals = $1,011.63       $1,094.9244   $1,094.93   $1,094.95   $1,095.10