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	$37.52	3.487%	$38.8283	$38.83	$38.85	$38.80
Purchase #2	$142.64	13.327%	$161.6496	$161.65	$161.65	$161.60
Purchase #3	$158.62	13.329%	$179.7625	$179.76	$179.75	$179.80
Purchase #4	$214.32	3.237%	$221.2575	$221.26	$221.25	$221.30
Purchase #5	$100.56	6.171%	$106.7656	$106.77	$106.75	$106.80
Purchase #6	$231.83	11.184%	$257.7579	$257.76	$257.75	$257.80
Purchase #7	$92.43	8.344%	$100.1424	$100.14	$100.15	$100.10
7 purchase totals =	$977.92		$1,066.1638	$1,066.17	$1,066.15	$1,066.20