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	$111.79	5.235%	$117.6422	$117.64	$117.65	$117.60
Purchase #2	$101.74	7.738%	$109.6126	$109.61	$109.60	$109.60
Purchase #3	$61.47	10.239%	$67.7639	$67.76	$67.75	$67.80
Purchase #4	$28.64	13.422%	$32.4841	$32.48	$32.50	$32.50
Purchase #5	$200.72	6.747%	$214.2626	$214.26	$214.25	$214.30
Purchase #6	$115.35	10.725%	$127.7213	$127.72	$127.70	$127.70
Purchase #7	$221.62	9.571%	$242.8313	$242.83	$242.85	$242.80
7 purchase totals =	$841.33		$912.3180	$912.30	$912.30	$912.30