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	$27.41	3.271%	$28.3066	$28.31	$28.30	$28.30
Purchase #2	$18.40	4.371%	$19.2043	$19.20	$19.20	$19.20
Purchase #3	$100.47	11.606%	$112.1305	$112.13	$112.15	$112.10
Purchase #4	$230.43	13.830%	$262.2985	$262.30	$262.30	$262.30
Purchase #5	$197.56	7.286%	$211.9542	$211.95	$211.95	$212.00
Purchase #6	$151.94	4.495%	$158.7697	$158.77	$158.75	$158.80
Purchase #7	$127.71	11.846%	$142.8385	$142.84	$142.85	$142.80
7 purchase totals =	$853.92		$935.5023	$935.50	$935.50	$935.50