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	$235.68	12.624%	$265.4322	$265.43	$265.45	$265.40
Purchase #2	$74.95	4.127%	$78.0432	$78.04	$78.05	$78.00
Purchase #3	$53.40	10.193%	$58.8431	$58.84	$58.85	$58.80
Purchase #4	$76.76	13.115%	$86.8271	$86.83	$86.85	$86.80
Purchase #5	$105.50	5.514%	$111.3173	$111.32	$111.30	$111.30
Purchase #6	$42.70	11.754%	$47.719	$47.72	$47.70	$47.70
Purchase #7	$193.76	12.251%	$217.4975	$217.50	$217.50	$217.50
7 purchase totals =	$782.75		$865.6794	$865.68	$865.70	$865.50