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	$62.68	8.223%	$67.8342	$67.83	$67.85	$67.80
Purchase #2	$100.42	3.287%	$103.7208	$103.72	$103.70	$103.70
Purchase #3	$74.63	7.450%	$80.1899	$80.19	$80.20	$80.20
Purchase #4	$101.64	9.814%	$111.6149	$111.61	$111.60	$111.60
Purchase #5	$229.96	7.658%	$247.5703	$247.57	$247.55	$247.60
Purchase #6	$156.32	13.255%	$177.0402	$177.04	$177.05	$177.00
Purchase #7	$52.45	4.773%	$54.9534	$54.95	$54.95	$55.00
7 purchase totals =	$778.10		$842.9237	$842.91	$842.90	$842.90