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	5.751%	$193.4715	$193.47	$193.45	$193.50
Purchase #2	$50.72	11.617%	$56.6121	$56.61	$56.60	$56.60
Purchase #3	$19.32	4.346%	$20.1596	$20.16	$20.15	$20.20
Purchase #4	$65.64	10.314%	$72.4101	$72.41	$72.40	$72.40
Purchase #5	$62.96	4.193%	$65.5999	$65.60	$65.60	$65.60
Purchase #6	$229.89	6.444%	$244.7041	$244.70	$244.70	$244.70
Purchase #7	$28.64	5.852%	$30.316	$30.32	$30.30	$30.30
7 purchase totals =	$640.12		$683.2733	$683.27	$683.20	$683.30