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	$142.64	4.358%	$148.8563	$148.86	$148.85	$148.90
Purchase #2	$163.78	7.729%	$176.4386	$176.44	$176.45	$176.40
Purchase #3	$109.35	3.259%	$112.9137	$112.91	$112.90	$112.90
Purchase #4	$131.95	3.724%	$136.8638	$136.86	$136.85	$136.90
Purchase #5	$164.45	10.719%	$182.0774	$182.08	$182.10	$182.10
Purchase #6	$67.75	5.544%	$71.5061	$71.51	$71.50	$71.50
Purchase #7	$150.98	3.856%	$156.8018	$156.80	$156.80	$156.80
7 purchase totals =	$930.90		$985.4577	$985.46	$985.45	$985.50