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	$48.66	6.218%	$51.6857	$51.69	$51.70	$51.70
Purchase #2	$10.51	5.783%	$11.1178	$11.12	$11.10	$11.10
Purchase #3	$94.32	4.103%	$98.1899	$98.19	$98.20	$98.20
Purchase #4	$54.29	9.853%	$59.6392	$59.64	$59.65	$59.60
Purchase #5	$157.89	9.178%	$172.3811	$172.38	$172.40	$172.40
Purchase #6	$94.60	11.335%	$105.3229	$105.32	$105.30	$105.30
Purchase #7	$147.68	9.788%	$162.1349	$162.13	$162.15	$162.10
7 purchase totals =	$607.95		$660.4715	$660.47	$660.50	$660.40