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	$156.99	10.491%	$173.4598	$173.46	$173.45	$173.50
Purchase #2	$196.71	3.789%	$204.1633	$204.16	$204.15	$204.20
Purchase #3	$97.62	13.733%	$111.0262	$111.03	$111.05	$111.00
Purchase #4	$92.39	13.718%	$105.0641	$105.06	$105.05	$105.10
Purchase #5	$78.71	3.856%	$81.7451	$81.75	$81.75	$81.70
Purchase #6	$228.90	7.198%	$245.3762	$245.38	$245.40	$245.40
Purchase #7	$150.68	4.383%	$157.2843	$157.28	$157.30	$157.30
7 purchase totals =	$1,002.00		$1,078.1190	$1,078.12	$1,078.15	$1,078.20