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	$39.66	5.463%	$41.8266	$41.83	$41.85	$41.80
Purchase #2	$68.67	4.421%	$71.7059	$71.71	$71.70	$71.70
Purchase #3	$105.83	5.782%	$111.9491	$111.95	$111.95	$111.90
Purchase #4	$219.25	10.212%	$241.6398	$241.64	$241.65	$241.60
Purchase #5	$111.50	6.509%	$118.7575	$118.76	$118.75	$118.80
Purchase #6	$165.72	9.784%	$181.934	$181.93	$181.95	$181.90
Purchase #7	$167.57	5.390%	$176.602	$176.60	$176.60	$176.60
7 purchase totals =	$878.20		$944.4149	$944.42	$944.45	$944.30