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	$152.44	6.572%	$162.4584	$162.46	$162.45	$162.50
Purchase #2	$111.94	11.189%	$124.465	$124.47	$124.45	$124.50
Purchase #3	$18.41	7.192%	$19.734	$19.73	$19.75	$19.70
Purchase #4	$143.50	10.174%	$158.0997	$158.10	$158.10	$158.10
Purchase #5	$93.91	3.481%	$97.179	$97.18	$97.20	$97.20
Purchase #6	$151.51	4.204%	$157.8795	$157.88	$157.90	$157.90
Purchase #7	$111.41	10.841%	$123.488	$123.49	$123.50	$123.50
7 purchase totals =	$783.12		$843.3036	$843.31	$843.35	$843.40