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	$147.81	5.124%	$155.3838	$155.38	$155.40	$155.40
Purchase #2	$50.68	7.376%	$54.4182	$54.42	$54.40	$54.40
Purchase #3	$99.82	11.644%	$111.443	$111.44	$111.45	$111.40
Purchase #4	$241.74	5.422%	$254.8471	$254.85	$254.85	$254.80
Purchase #5	$173.85	7.385%	$186.6888	$186.69	$186.70	$186.70
Purchase #6	$18.81	7.332%	$20.1891	$20.19	$20.20	$20.20
Purchase #7	$207.32	13.664%	$235.6482	$235.65	$235.65	$235.60
7 purchase totals =	$940.03		$1,018.6182	$1,018.62	$1,018.65	$1,018.50