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	$133.99	10.196%	$147.6516	$147.65	$147.65	$147.70
Purchase #2	$230.51	11.274%	$256.4977	$256.50	$256.50	$256.50
Purchase #3	$117.43	5.159%	$123.4882	$123.49	$123.50	$123.50
Purchase #4	$133.78	13.419%	$151.7319	$151.73	$151.75	$151.70
Purchase #5	$46.95	3.178%	$48.4421	$48.44	$48.45	$48.40
Purchase #6	$83.60	9.850%	$91.8346	$91.83	$91.85	$91.80
Purchase #7	$151.83	4.564%	$158.7595	$158.76	$158.75	$158.80
7 purchase totals =	$898.09		$978.4056	$978.40	$978.45	$978.40