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	$219.91	9.304%	$240.3704	$240.37	$240.35	$240.40
Purchase #2	$95.52	13.471%	$108.3875	$108.39	$108.40	$108.40
Purchase #3	$116.95	12.230%	$131.253	$131.25	$131.25	$131.30
Purchase #4	$75.74	9.271%	$82.7619	$82.76	$82.75	$82.80
Purchase #5	$240.37	5.142%	$252.7298	$252.73	$252.75	$252.70
Purchase #6	$127.42	4.343%	$132.9539	$132.95	$132.95	$133.00
Purchase #7	$108.77	4.341%	$113.4917	$113.49	$113.50	$113.50
7 purchase totals =	$984.68		$1,061.9482	$1,061.94	$1,061.95	$1,062.10