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	$56.99	9.335%	$62.31	$62.31	$62.30	$62.30
Purchase #2	$101.46	9.789%	$111.3919	$111.39	$111.40	$111.40
Purchase #3	$74.26	8.724%	$80.7384	$80.74	$80.75	$80.70
Purchase #4	$151.25	4.852%	$158.5887	$158.59	$158.60	$158.60
Purchase #5	$79.25	10.150%	$87.2939	$87.29	$87.30	$87.30
Purchase #6	$178.56	6.600%	$190.345	$190.35	$190.35	$190.30
Purchase #7	$63.58	3.300%	$65.6781	$65.68	$65.70	$65.70
7 purchase totals =	$705.35		$756.3460	$756.35	$756.40	$756.30