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	$98.92	6.422%	$105.2726	$105.27	$105.25	$105.30
Purchase #2	$34.82	9.394%	$38.091	$38.09	$38.10	$38.10
Purchase #3	$139.78	3.315%	$144.4137	$144.41	$144.40	$144.40
Purchase #4	$12.47	9.219%	$13.6196	$13.62	$13.60	$13.60
Purchase #5	$143.94	5.490%	$151.8423	$151.84	$151.85	$151.80
Purchase #6	$171.82	4.627%	$179.7701	$179.77	$179.75	$179.80
Purchase #7	$204.31	8.374%	$221.4189	$221.42	$221.40	$221.40
7 purchase totals =	$806.06		$854.4282	$854.42	$854.35	$854.40