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	$32.32	7.677%	$34.8012	$34.80	$34.80	$34.80
Purchase #2	$240.95	10.218%	$265.5703	$265.57	$265.55	$265.60
Purchase #3	$92.61	12.406%	$104.0992	$104.10	$104.10	$104.10
Purchase #4	$122.26	4.473%	$127.7287	$127.73	$127.75	$127.70
Purchase #5	$54.93	5.407%	$57.9001	$57.90	$57.90	$57.90
Purchase #6	$104.58	3.256%	$107.9851	$107.99	$108.00	$108.00
Purchase #7	$173.39	13.337%	$196.515	$196.52	$196.50	$196.50
7 purchase totals =	$821.04		$894.5996	$894.61	$894.60	$894.60