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	$77.43	6.564%	$82.5125	$82.51	$82.50	$82.50
Purchase #2	$190.63	5.221%	$200.5828	$200.58	$200.60	$200.60
Purchase #3	$143.71	6.559%	$153.1359	$153.14	$153.15	$153.10
Purchase #4	$116.75	12.251%	$131.053	$131.05	$131.05	$131.10
Purchase #5	$98.91	11.568%	$110.3519	$110.35	$110.35	$110.40
Purchase #6	$18.53	5.335%	$19.5186	$19.52	$19.50	$19.50
Purchase #7	$53.63	12.378%	$60.2683	$60.27	$60.25	$60.30
7 purchase totals =	$699.59		$757.4230	$757.42	$757.40	$757.50