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	$197.85	12.292%	$222.1697	$222.17	$222.15	$222.20
Purchase #2	$39.82	6.753%	$42.509	$42.51	$42.50	$42.50
Purchase #3	$24.94	5.353%	$26.275	$26.28	$26.30	$26.30
Purchase #4	$57.92	13.823%	$65.9263	$65.93	$65.95	$65.90
Purchase #5	$238.99	11.330%	$266.0676	$266.07	$266.05	$266.10
Purchase #6	$232.91	9.688%	$255.4743	$255.47	$255.45	$255.50
Purchase #7	$154.28	12.390%	$173.3953	$173.40	$173.40	$173.40
7 purchase totals =	$946.71		$1,051.8172	$1,051.83	$1,051.80	$1,051.90