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 $207.92   8.549%   $225.6951   $225.70   $225.70   $225.70  
  Purchase #2 $230.63   9.159%   $251.7534   $251.75   $251.75   $251.80  
  Purchase #3 $82.40   5.103%   $86.6049   $86.60   $86.60   $86.60  
  Purchase #4 $108.89   5.742%   $115.1425   $115.14   $115.15   $115.10  
  Purchase #5 $69.57   13.753%   $79.138   $79.14   $79.15   $79.10  
  Purchase #6 $185.49   5.540%   $195.7661   $195.77   $195.75   $195.80  
  Purchase #7 $141.76   11.836%   $158.5387   $158.54   $158.55   $158.50  
  7 purchase totals = $1,026.66       $1,112.6387   $1,112.64   $1,112.65   $1,112.60