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	$216.35	5.856%	$229.0195	$229.02	$229.00	$229.00
Purchase #2	$105.51	5.447%	$111.2571	$111.26	$111.25	$111.30
Purchase #3	$214.75	11.158%	$238.7118	$238.71	$238.70	$238.70
Purchase #4	$62.34	13.562%	$70.7946	$70.79	$70.80	$70.80
Purchase #5	$162.47	10.483%	$179.5017	$179.50	$179.50	$179.50
Purchase #6	$127.35	11.235%	$141.6578	$141.66	$141.65	$141.70
Purchase #7	$89.91	9.522%	$98.4712	$98.47	$98.45	$98.50
7 purchase totals =	$978.68		$1,069.4137	$1,069.41	$1,069.35	$1,069.50