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 $166.44   5.860%   $176.1934   $176.19   $176.20   $176.20  
  Purchase #2 $140.88   8.844%   $153.3394   $153.34   $153.35   $153.30  
  Purchase #3 $215.58   10.285%   $237.7524   $237.75   $237.75   $237.80  
  Purchase #4 $182.27   7.321%   $195.614   $195.61   $195.60   $195.60  
  Purchase #5 $224.53   6.769%   $239.7284   $239.73   $239.75   $239.70  
  Purchase #6 $49.62   13.674%   $56.405   $56.41   $56.40   $56.40  
  Purchase #7 $97.57   6.545%   $103.956   $103.96   $103.95   $104.00  
  7 purchase totals = $1,076.89       $1,162.9886   $1,162.99   $1,163.00   $1,163.00