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	$133.62	8.474%	$144.943	$144.94	$144.95	$144.90
Purchase #2	$166.29	5.494%	$175.426	$175.43	$175.45	$175.40
Purchase #3	$139.90	8.247%	$151.4376	$151.44	$151.45	$151.40
Purchase #4	$125.78	13.364%	$142.5892	$142.59	$142.60	$142.60
Purchase #5	$73.65	6.663%	$78.5573	$78.56	$78.55	$78.60
Purchase #6	$241.95	4.246%	$252.2232	$252.22	$252.20	$252.20
Purchase #7	$250.86	8.220%	$271.4807	$271.48	$271.50	$271.50
7 purchase totals =	$1,132.05		$1,216.6570	$1,216.66	$1,216.70	$1,216.60