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 $208.69   7.742%   $224.8468   $224.85   $224.85   $224.80  
  Purchase #2 $16.93   10.797%   $18.7579   $18.76   $18.75   $18.80  
  Purchase #3 $216.88   3.666%   $224.8308   $224.83   $224.85   $224.80  
  Purchase #4 $28.59   8.217%   $30.9392   $30.94   $30.95   $30.90  
  Purchase #5 $157.90   7.726%   $170.0994   $170.10   $170.10   $170.10  
  Purchase #6 $149.74   9.710%   $164.2798   $164.28   $164.30   $164.30  
  Purchase #7 $223.34   8.601%   $242.5495   $242.55   $242.55   $242.50  
  7 purchase totals = $1,002.07       $1,076.3034   $1,076.31   $1,076.35   $1,076.20