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 $146.42   11.151%   $162.7473   $162.75   $162.75   $162.70  
  Purchase #2 $22.63   7.369%   $24.2976   $24.30   $24.30   $24.30  
  Purchase #3 $29.59   9.175%   $32.3049   $32.30   $32.30   $32.30  
  Purchase #4 $131.64   8.871%   $143.3178   $143.32   $143.30   $143.30  
  Purchase #5 $177.50   8.169%   $192   $192.00   $192.00   $192.00  
  Purchase #6 $239.76   9.572%   $262.7098   $262.71   $262.70   $262.70  
  Purchase #7 $190.56   9.460%   $208.587   $208.59   $208.60   $208.60  
  7 purchase totals = $938.10       $1,025.9644   $1,025.97   $1,025.95   $1,025.90