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 $214.86   5.211%   $226.0564   $226.06   $226.05   $226.10  
  Purchase #2 $134.26   10.295%   $148.0821   $148.08   $148.10   $148.10  
  Purchase #3 $239.64   4.170%   $249.633   $249.63   $249.65   $249.60  
  Purchase #4 $119.63   5.615%   $126.3472   $126.35   $126.35   $126.30  
  Purchase #5 $113.40   10.167%   $124.9294   $124.93   $124.95   $124.90  
  Purchase #6 $190.78   11.766%   $213.2272   $213.23   $213.25   $213.20  
  Purchase #7 $160.99   6.787%   $171.9164   $171.92   $171.90   $171.90  
  7 purchase totals = $1,173.56       $1,260.1917   $1,260.20   $1,260.25   $1,260.10