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 $69.36   8.652%   $75.361   $75.36   $75.35   $75.40  
  Purchase #2 $105.32   6.209%   $111.8593   $111.86   $111.85   $111.90  
  Purchase #3 $157.76   4.321%   $164.5768   $164.58   $164.60   $164.60  
  Purchase #4 $247.48   10.834%   $274.292   $274.29   $274.30   $274.30  
  Purchase #5 $178.65   7.815%   $192.6115   $192.61   $192.60   $192.60  
  Purchase #6 $8.64   11.598%   $9.6421   $9.64   $9.65   $9.60  
  Purchase #7 $117.48   4.628%   $122.917   $122.92   $122.90   $122.90  
  7 purchase totals = $884.69       $951.2597   $951.26   $951.25   $951.30