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	$228.91	9.692%	$251.096	$251.10	$251.10	$251.10
Purchase #2	$74.46	9.644%	$81.6409	$81.64	$81.65	$81.60
Purchase #3	$107.84	3.251%	$111.3459	$111.35	$111.35	$111.30
Purchase #4	$62.83	7.588%	$67.5975	$67.60	$67.60	$67.60
Purchase #5	$145.25	3.657%	$150.5618	$150.56	$150.55	$150.60
Purchase #6	$40.95	13.371%	$46.4254	$46.43	$46.45	$46.40
Purchase #7	$25.70	5.232%	$27.0446	$27.04	$27.05	$27.00
7 purchase totals =	$685.94		$735.7121	$735.72	$735.75	$735.60