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	$61.61	8.546%	$66.8752	$66.88	$66.90	$66.90
Purchase #2	$243.99	4.794%	$255.6869	$255.69	$255.70	$255.70
Purchase #3	$242.71	5.411%	$255.843	$255.84	$255.85	$255.80
Purchase #4	$104.55	7.151%	$112.0264	$112.03	$112.05	$112.00
Purchase #5	$11.35	9.791%	$12.4613	$12.46	$12.45	$12.50
Purchase #6	$196.77	3.205%	$203.0765	$203.08	$203.10	$203.10
Purchase #7	$184.25	3.255%	$190.2473	$190.25	$190.25	$190.20
7 purchase totals =	$1,045.23		$1,096.2166	$1,096.23	$1,096.30	$1,096.20