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	$60.39	8.256%	$65.3758	$65.38	$65.40	$65.40
Purchase #2	$105.72	6.683%	$112.7853	$112.79	$112.80	$112.80
Purchase #3	$204.82	8.419%	$222.0638	$222.06	$222.05	$222.10
Purchase #4	$55.85	10.610%	$61.7757	$61.78	$61.80	$61.80
Purchase #5	$32.44	3.820%	$33.6792	$33.68	$33.70	$33.70
Purchase #6	$121.60	10.167%	$133.9631	$133.96	$133.95	$134.00
Purchase #7	$138.77	11.445%	$154.6522	$154.65	$154.65	$154.70
7 purchase totals =	$719.59		$784.2951	$784.30	$784.35	$784.50