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 $23.96   8.365%   $25.9643   $25.96   $25.95   $26.00  
  Purchase #2 $86.38   6.530%   $92.0206   $92.02   $92.00   $92.00  
  Purchase #3 $247.77   5.835%   $262.2274   $262.23   $262.25   $262.20  
  Purchase #4 $63.65   10.567%   $70.3759   $70.38   $70.40   $70.40  
  Purchase #5 $92.42   13.690%   $105.0723   $105.07   $105.05   $105.10  
  Purchase #6 $47.68   7.558%   $51.2837   $51.28   $51.30   $51.30  
  Purchase #7 $63.34   3.153%   $65.3371   $65.34   $65.35   $65.30  
  7 purchase totals = $625.20       $672.2813   $672.28   $672.30   $672.30