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 $195.56   6.460%   $208.1932   $208.19   $208.20   $208.20  
  Purchase #2 $38.92   7.116%   $41.6895   $41.69   $41.70   $41.70  
  Purchase #3 $165.99   5.181%   $174.5899   $174.59   $174.60   $174.60  
  Purchase #4 $215.35   9.798%   $236.45   $236.45   $236.45   $236.50  
  Purchase #5 $175.44   8.249%   $189.912   $189.91   $189.90   $189.90  
  Purchase #6 $30.70   4.705%   $32.1444   $32.14   $32.15   $32.10  
  Purchase #7 $209.91   3.633%   $217.536   $217.54   $217.55   $217.50  
  7 purchase totals = $1,031.87       $1,100.5150   $1,100.51   $1,100.55   $1,100.50