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	$114.51	10.830%	$126.9114	$126.91	$126.90	$126.90
Purchase #2	$34.68	6.833%	$37.0497	$37.05	$37.05	$37.00
Purchase #3	$137.44	13.255%	$155.6577	$155.66	$155.65	$155.70
Purchase #4	$117.33	9.538%	$128.5209	$128.52	$128.50	$128.50
Purchase #5	$138.98	4.828%	$145.69	$145.69	$145.70	$145.70
Purchase #6	$189.39	13.609%	$215.1641	$215.16	$215.15	$215.20
Purchase #7	$92.84	7.634%	$99.9274	$99.93	$99.95	$99.90
7 purchase totals =	$825.17		$908.9212	$908.92	$908.90	$908.90