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	$166.60	5.456%	$175.6897	$175.69	$175.70	$175.70
Purchase #2	$80.42	13.725%	$91.4576	$91.46	$91.45	$91.50
Purchase #3	$28.29	7.110%	$30.3014	$30.30	$30.30	$30.30
Purchase #4	$49.70	8.656%	$54.002	$54.00	$54.00	$54.00
Purchase #5	$45.62	13.289%	$51.6824	$51.68	$51.70	$51.70
Purchase #6	$17.40	6.364%	$18.5073	$18.51	$18.50	$18.50
Purchase #7	$173.26	13.366%	$196.4179	$196.42	$196.40	$196.40
7 purchase totals =	$561.29		$618.0583	$618.06	$618.05	$618.10