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 $182.95   9.220%   $199.818   $199.82   $199.80   $199.80  
  Purchase #2 $130.84   3.678%   $135.6523   $135.65   $135.65   $135.70  
  Purchase #3 $218.82   13.341%   $248.0128   $248.01   $248.00   $248.00  
  Purchase #4 $36.31   12.837%   $40.9711   $40.97   $40.95   $41.00  
  Purchase #5 $70.51   8.677%   $76.6282   $76.63   $76.65   $76.60  
  Purchase #6 $208.87   3.177%   $215.5058   $215.51   $215.50   $215.50  
  Purchase #7 $226.41   13.255%   $256.4206   $256.42   $256.40   $256.40  
  7 purchase totals = $1,074.71       $1,173.0088   $1,173.01   $1,172.95   $1,173.00