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	$48.92	9.150%	$53.3962	$53.40	$53.40	$53.40
Purchase #2	$60.44	10.614%	$66.8551	$66.86	$66.85	$66.90
Purchase #3	$70.57	11.803%	$78.8994	$78.90	$78.90	$78.90
Purchase #4	$159.94	8.603%	$173.6996	$173.70	$173.70	$173.70
Purchase #5	$209.64	10.550%	$231.757	$231.76	$231.75	$231.80
Purchase #6	$161.86	3.218%	$167.0687	$167.07	$167.05	$167.10
Purchase #7	$187.87	4.412%	$196.1588	$196.16	$196.15	$196.20
7 purchase totals =	$899.24		$967.8348	$967.85	$967.80	$968.00