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	$129.83	11.810%	$145.1629	$145.16	$145.15	$145.20
Purchase #2	$158.75	4.163%	$165.3588	$165.36	$165.35	$165.40
Purchase #3	$100.88	10.240%	$111.2101	$111.21	$111.20	$111.20
Purchase #4	$114.70	10.707%	$126.9809	$126.98	$127.00	$127.00
Purchase #5	$199.93	12.300%	$224.5214	$224.52	$224.50	$224.50
Purchase #6	$148.69	4.418%	$155.2591	$155.26	$155.25	$155.30
Purchase #7	$236.62	12.555%	$266.3276	$266.33	$266.35	$266.30
7 purchase totals =	$1,089.40		$1,194.8208	$1,194.82	$1,194.80	$1,194.90