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	$234.41	10.157%	$258.219	$258.22	$258.20	$258.20
Purchase #2	$100.71	4.745%	$105.4887	$105.49	$105.50	$105.50
Purchase #3	$147.92	8.583%	$160.616	$160.62	$160.60	$160.60
Purchase #4	$228.96	4.711%	$239.7463	$239.75	$239.75	$239.70
Purchase #5	$87.28	9.542%	$95.6083	$95.61	$95.60	$95.60
Purchase #6	$191.78	3.501%	$198.4942	$198.49	$198.50	$198.50
Purchase #7	$230.42	5.307%	$242.6484	$242.65	$242.65	$242.60
7 purchase totals =	$1,221.48		$1,300.8209	$1,300.83	$1,300.80	$1,300.70