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	$97.38	11.615%	$108.6907	$108.69	$108.70	$108.70
Purchase #2	$100.76	10.845%	$111.6874	$111.69	$111.70	$111.70
Purchase #3	$190.69	6.528%	$203.1382	$203.14	$203.15	$203.10
Purchase #4	$116.98	13.285%	$132.5208	$132.52	$132.50	$132.50
Purchase #5	$33.60	12.769%	$37.8904	$37.89	$37.90	$37.90
Purchase #6	$150.99	9.598%	$165.482	$165.48	$165.50	$165.50
Purchase #7	$83.82	5.305%	$88.2667	$88.27	$88.25	$88.30
7 purchase totals =	$774.22		$847.6762	$847.68	$847.70	$847.70