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	$152.87	8.794%	$166.3134	$166.31	$166.30	$166.30
Purchase #2	$9.78	5.422%	$10.3103	$10.31	$10.30	$10.30
Purchase #3	$207.37	6.560%	$220.9735	$220.97	$220.95	$221.00
Purchase #4	$9.72	7.319%	$10.4314	$10.43	$10.45	$10.40
Purchase #5	$118.68	7.146%	$127.1609	$127.16	$127.15	$127.20
Purchase #6	$229.59	7.828%	$247.5623	$247.56	$247.55	$247.60
Purchase #7	$216.77	4.233%	$225.9459	$225.95	$225.95	$225.90
7 purchase totals =	$944.78		$1,008.6977	$1,008.69	$1,008.65	$1,008.70