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	$217.27	5.303%	$228.7918	$228.79	$228.80	$228.80
Purchase #2	$159.39	3.730%	$165.3352	$165.34	$165.35	$165.30
Purchase #3	$9.44	10.730%	$10.4529	$10.45	$10.45	$10.50
Purchase #4	$50.27	7.181%	$53.8799	$53.88	$53.90	$53.90
Purchase #5	$17.85	11.337%	$19.8737	$19.87	$19.85	$19.90
Purchase #6	$98.33	5.275%	$103.5169	$103.52	$103.50	$103.50
Purchase #7	$129.43	6.149%	$137.3887	$137.39	$137.40	$137.40
7 purchase totals =	$681.98		$719.2391	$719.24	$719.25	$719.30