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	$229.70	11.853%	$256.9263	$256.93	$256.95	$256.90
Purchase #2	$165.45	4.716%	$173.2526	$173.25	$173.25	$173.30
Purchase #3	$29.81	12.221%	$33.4531	$33.45	$33.45	$33.50
Purchase #4	$110.69	8.534%	$120.1363	$120.14	$120.15	$120.10
Purchase #5	$33.26	11.244%	$36.9998	$37.00	$37.00	$37.00
Purchase #6	$130.78	11.328%	$145.5948	$145.59	$145.60	$145.60
Purchase #7	$160.95	12.683%	$181.3633	$181.36	$181.35	$181.40
7 purchase totals =	$860.64		$947.7262	$947.72	$947.75	$947.80