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 $237.44   10.551%   $262.4923   $262.49   $262.50   $262.50  
  Purchase #2 $204.71   8.297%   $221.6948   $221.69   $221.70   $221.70  
  Purchase #3 $46.65   6.170%   $49.5283   $49.53   $49.55   $49.50  
  Purchase #4 $32.87   9.483%   $35.9871   $35.99   $36.00   $36.00  
  Purchase #5 $124.43   12.850%   $140.4193   $140.42   $140.40   $140.40  
  Purchase #6 $121.36   10.753%   $134.4098   $134.41   $134.40   $134.40  
  Purchase #7 $192.68   5.565%   $203.4026   $203.40   $203.40   $203.40  
  7 purchase totals = $960.14       $1,047.9342   $1,047.93   $1,047.95   $1,047.90