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	$85.52	8.250%	$92.5754	$92.58	$92.60	$92.60
Purchase #2	$115.64	9.871%	$127.0548	$127.05	$127.05	$127.10
Purchase #3	$118.37	10.812%	$131.1682	$131.17	$131.15	$131.20
Purchase #4	$151.85	8.842%	$165.2766	$165.28	$165.30	$165.30
Purchase #5	$47.47	4.121%	$49.4262	$49.43	$49.45	$49.40
Purchase #6	$9.63	5.352%	$10.1454	$10.15	$10.15	$10.10
Purchase #7	$44.69	4.821%	$46.8445	$46.84	$46.85	$46.80
7 purchase totals =	$573.17		$622.4911	$622.50	$622.55	$622.50