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	$234.90	11.614%	$262.1813	$262.18	$262.20	$262.20
Purchase #2	$231.32	8.444%	$250.8527	$250.85	$250.85	$250.90
Purchase #3	$111.56	13.527%	$126.6507	$126.65	$126.65	$126.70
Purchase #4	$44.59	5.526%	$47.054	$47.05	$47.05	$47.10
Purchase #5	$13.61	9.239%	$14.8674	$14.87	$14.85	$14.90
Purchase #6	$122.39	4.150%	$127.4692	$127.47	$127.45	$127.50
Purchase #7	$52.33	8.173%	$56.6069	$56.61	$56.60	$56.60
7 purchase totals =	$810.70		$885.6822	$885.68	$885.65	$885.90