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	$244.68	4.652%	$256.0625	$256.06	$256.05	$256.10
Purchase #2	$172.79	13.669%	$196.4087	$196.41	$196.40	$196.40
Purchase #3	$114.57	5.847%	$121.2689	$121.27	$121.25	$121.30
Purchase #4	$91.36	9.563%	$100.0968	$100.10	$100.10	$100.10
Purchase #5	$153.38	5.348%	$161.5828	$161.58	$161.60	$161.60
Purchase #6	$132.47	9.289%	$144.7751	$144.78	$144.80	$144.80
Purchase #7	$109.89	12.161%	$123.2537	$123.25	$123.25	$123.30
7 purchase totals =	$1,019.14		$1,103.4485	$1,103.45	$1,103.45	$1,103.60