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	$18.96	5.191%	$19.9442	$19.94	$19.95	$19.90
Purchase #2	$127.53	5.802%	$134.9293	$134.93	$134.95	$134.90
Purchase #3	$174.54	5.659%	$184.4172	$184.42	$184.40	$184.40
Purchase #4	$136.76	3.536%	$141.5958	$141.60	$141.60	$141.60
Purchase #5	$210.90	9.446%	$230.8216	$230.82	$230.80	$230.80
Purchase #6	$150.45	13.324%	$170.496	$170.50	$170.50	$170.50
Purchase #7	$126.82	8.462%	$137.5515	$137.55	$137.55	$137.60
7 purchase totals =	$945.96		$1,019.7556	$1,019.76	$1,019.75	$1,019.70