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	$152.82	8.182%	$165.3237	$165.32	$165.30	$165.30
Purchase #2	$186.49	11.621%	$208.162	$208.16	$208.15	$208.20
Purchase #3	$163.42	6.170%	$173.503	$173.50	$173.50	$173.50
Purchase #4	$228.25	12.639%	$257.0985	$257.10	$257.10	$257.10
Purchase #5	$151.51	10.769%	$167.8261	$167.83	$167.85	$167.80
Purchase #6	$136.89	5.585%	$144.5353	$144.54	$144.55	$144.50
Purchase #7	$95.44	6.339%	$101.4899	$101.49	$101.50	$101.50
7 purchase totals =	$1,114.82		$1,217.9385	$1,217.94	$1,217.95	$1,217.90