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	$197.27	12.602%	$222.13	$222.13	$222.15	$222.10
Purchase #2	$158.51	9.281%	$173.2213	$173.22	$173.20	$173.20
Purchase #3	$18.81	4.534%	$19.6628	$19.66	$19.65	$19.70
Purchase #4	$93.84	7.111%	$100.513	$100.51	$100.50	$100.50
Purchase #5	$148.50	5.314%	$156.3913	$156.39	$156.40	$156.40
Purchase #6	$204.52	7.314%	$219.4786	$219.48	$219.50	$219.50
Purchase #7	$17.61	7.145%	$18.8682	$18.87	$18.85	$18.90
7 purchase totals =	$839.06		$910.2652	$910.26	$910.25	$910.30