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	$67.41	9.152%	$73.5794	$73.58	$73.60	$73.60
Purchase #2	$50.70	12.160%	$56.8651	$56.87	$56.85	$56.90
Purchase #3	$175.72	10.769%	$194.6433	$194.64	$194.65	$194.60
Purchase #4	$205.91	5.152%	$216.5185	$216.52	$216.50	$216.50
Purchase #5	$98.67	13.478%	$111.9687	$111.97	$111.95	$112.00
Purchase #6	$117.52	8.398%	$127.3893	$127.39	$127.40	$127.40
Purchase #7	$151.61	13.732%	$172.4291	$172.43	$172.45	$172.40
7 purchase totals =	$867.54		$953.3934	$953.40	$953.40	$953.40