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	$153.28	3.486%	$158.6233	$158.62	$158.60	$158.60
Purchase #2	$205.76	6.162%	$218.4389	$218.44	$218.45	$218.40
Purchase #3	$23.37	9.152%	$25.5088	$25.51	$25.50	$25.50
Purchase #4	$212.63	9.808%	$233.4848	$233.48	$233.50	$233.50
Purchase #5	$211.27	5.425%	$222.7314	$222.73	$222.75	$222.70
Purchase #6	$54.34	10.518%	$60.0555	$60.06	$60.05	$60.10
Purchase #7	$29.72	13.157%	$33.6303	$33.63	$33.65	$33.60
7 purchase totals =	$890.37		$952.4730	$952.47	$952.50	$952.40