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	$13.37	6.651%	$14.2592	$14.26	$14.25	$14.30
Purchase #2	$104.90	6.510%	$111.729	$111.73	$111.75	$111.70
Purchase #3	$14.90	5.406%	$15.7055	$15.71	$15.70	$15.70
Purchase #4	$8.54	11.639%	$9.534	$9.53	$9.55	$9.50
Purchase #5	$164.42	4.243%	$171.3963	$171.40	$171.40	$171.40
Purchase #6	$234.54	4.246%	$244.4986	$244.50	$244.50	$244.50
Purchase #7	$50.76	13.203%	$57.4618	$57.46	$57.45	$57.50
7 purchase totals =	$591.43		$624.5844	$624.59	$624.60	$624.60