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	$211.35	10.528%	$233.6009	$233.60	$233.60	$233.60
Purchase #2	$186.73	3.428%	$193.1311	$193.13	$193.15	$193.10
Purchase #3	$121.69	7.235%	$130.4943	$130.49	$130.50	$130.50
Purchase #4	$110.72	6.479%	$117.8935	$117.89	$117.90	$117.90
Purchase #5	$132.90	10.538%	$146.905	$146.91	$146.90	$146.90
Purchase #6	$122.51	4.369%	$127.8625	$127.86	$127.85	$127.90
Purchase #7	$71.25	10.479%	$78.7163	$78.72	$78.70	$78.70
7 purchase totals =	$957.15		$1,028.6036	$1,028.60	$1,028.60	$1,028.60