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	$143.51	7.744%	$154.6234	$154.62	$154.60	$154.60
Purchase #2	$186.52	12.735%	$210.2733	$210.27	$210.25	$210.30
Purchase #3	$166.30	4.225%	$173.3262	$173.33	$173.35	$173.30
Purchase #4	$156.64	10.314%	$172.7958	$172.80	$172.80	$172.80
Purchase #5	$221.94	3.296%	$229.2551	$229.26	$229.25	$229.30
Purchase #6	$46.54	8.622%	$50.5527	$50.55	$50.55	$50.60
Purchase #7	$76.95	4.280%	$80.2435	$80.24	$80.25	$80.20
7 purchase totals =	$998.40		$1,071.0700	$1,071.07	$1,071.05	$1,071.10