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	$44.37	9.205%	$48.4543	$48.45	$48.45	$48.50
Purchase #2	$11.59	8.348%	$12.5575	$12.56	$12.55	$12.60
Purchase #3	$127.94	12.852%	$144.3828	$144.38	$144.40	$144.40
Purchase #4	$117.32	3.627%	$121.5752	$121.58	$121.60	$121.60
Purchase #5	$179.48	10.537%	$198.3918	$198.39	$198.40	$198.40
Purchase #6	$169.69	6.763%	$181.1661	$181.17	$181.15	$181.20
Purchase #7	$127.37	9.798%	$139.8497	$139.85	$139.85	$139.80
7 purchase totals =	$777.76		$846.3774	$846.38	$846.40	$846.50