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 $94.51   11.815%   $105.6764   $105.68   $105.70   $105.70  
  Purchase #2 $171.64   12.626%   $193.3113   $193.31   $193.30   $193.30  
  Purchase #3 $249.68   4.151%   $260.0442   $260.04   $260.05   $260.00  
  Purchase #4 $248.90   5.545%   $262.7015   $262.70   $262.70   $262.70  
  Purchase #5 $62.71   11.145%   $69.699   $69.70   $69.70   $69.70  
  Purchase #6 $74.31   11.160%   $82.603   $82.60   $82.60   $82.60  
  Purchase #7 $242.77   8.495%   $263.3933   $263.39   $263.40   $263.40  
  7 purchase totals = $1,144.52       $1,237.4287   $1,237.42   $1,237.45   $1,237.40