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	$87.41	8.325%	$94.6869	$94.69	$94.70	$94.70
Purchase #2	$18.41	5.687%	$19.457	$19.46	$19.45	$19.50
Purchase #3	$65.63	13.200%	$74.2932	$74.29	$74.30	$74.30
Purchase #4	$34.35	10.325%	$37.8966	$37.90	$37.90	$37.90
Purchase #5	$221.91	7.538%	$238.6376	$238.64	$238.65	$238.60
Purchase #6	$109.88	11.369%	$122.3723	$122.37	$122.35	$122.40
Purchase #7	$90.42	11.108%	$100.4639	$100.46	$100.45	$100.50
7 purchase totals =	$628.01		$687.8075	$687.81	$687.80	$687.90