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 $208.68   7.700%   $224.7484   $224.75   $224.75   $224.70  
  Purchase #2 $115.99   9.285%   $126.7597   $126.76   $126.75   $126.80  
  Purchase #3 $243.29   8.805%   $264.7117   $264.71   $264.70   $264.70  
  Purchase #4 $191.95   8.390%   $208.0546   $208.05   $208.05   $208.10  
  Purchase #5 $88.68   6.158%   $94.1409   $94.14   $94.15   $94.10  
  Purchase #6 $242.76   8.309%   $262.9309   $262.93   $262.95   $262.90  
  Purchase #7 $245.83   10.597%   $271.8806   $271.88   $271.90   $271.90  
  7 purchase totals = $1,337.18       $1,453.2268   $1,453.22   $1,453.25   $1,453.20