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	$165.25	13.539%	$187.6232	$187.62	$187.60	$187.60
Purchase #2	$43.38	11.400%	$48.3253	$48.33	$48.35	$48.30
Purchase #3	$131.95	8.509%	$143.1776	$143.18	$143.20	$143.20
Purchase #4	$246.64	6.261%	$262.0821	$262.08	$262.10	$262.10
Purchase #5	$127.76	5.137%	$134.323	$134.32	$134.30	$134.30
Purchase #6	$232.29	8.195%	$251.3262	$251.33	$251.35	$251.30
Purchase #7	$71.75	9.692%	$78.704	$78.70	$78.70	$78.70
7 purchase totals =	$1,019.02		$1,105.5614	$1,105.56	$1,105.60	$1,105.50