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 $241.54   8.664%   $262.467   $262.47   $262.45   $262.50  
  Purchase #2 $151.37   4.149%   $157.6503   $157.65   $157.65   $157.70  
  Purchase #3 $133.86   7.169%   $143.4564   $143.46   $143.45   $143.50  
  Purchase #4 $143.65   3.454%   $148.6117   $148.61   $148.60   $148.60  
  Purchase #5 $213.66   4.367%   $222.9905   $222.99   $223.00   $223.00  
  Purchase #6 $35.66   5.853%   $37.7472   $37.75   $37.75   $37.70  
  Purchase #7 $199.58   10.694%   $220.9231   $220.92   $220.90   $220.90  
  7 purchase totals = $1,119.32       $1,193.8462   $1,193.85   $1,193.80   $1,193.90