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	$234.38	8.728%	$254.8367	$254.84	$254.85	$254.80
Purchase #2	$179.72	9.130%	$196.1284	$196.13	$196.15	$196.10
Purchase #3	$143.65	8.255%	$155.5083	$155.51	$155.50	$155.50
Purchase #4	$54.69	3.266%	$56.4762	$56.48	$56.50	$56.50
Purchase #5	$233.83	13.425%	$265.2217	$265.22	$265.20	$265.20
Purchase #6	$241.45	12.361%	$271.2956	$271.30	$271.30	$271.30
Purchase #7	$99.31	6.163%	$105.4305	$105.43	$105.45	$105.40
7 purchase totals =	$1,187.03		$1,304.8974	$1,304.91	$1,304.95	$1,304.80