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 $193.92   5.844%   $205.2527   $205.25   $205.25   $205.30  
  Purchase #2 $118.99   13.868%   $135.4915   $135.49   $135.50   $135.50  
  Purchase #3 $73.69   3.525%   $76.2876   $76.29   $76.30   $76.30  
  Purchase #4 $244.85   10.259%   $269.9692   $269.97   $269.95   $270.00  
  Purchase #5 $182.54   6.805%   $194.9618   $194.96   $194.95   $195.00  
  Purchase #6 $206.40   5.712%   $218.1896   $218.19   $218.20   $218.20  
  Purchase #7 $239.57   9.405%   $262.1016   $262.10   $262.10   $262.10  
  7 purchase totals = $1,259.96       $1,362.2540   $1,362.25   $1,362.25   $1,362.40