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	$10.33	10.823%	$11.448	$11.45	$11.45	$11.40
Purchase #2	$54.90	3.815%	$56.9944	$56.99	$57.00	$57.00
Purchase #3	$127.60	12.759%	$143.8805	$143.88	$143.90	$143.90
Purchase #4	$160.85	4.717%	$168.4373	$168.44	$168.45	$168.40
Purchase #5	$53.53	10.339%	$59.0645	$59.06	$59.05	$59.10
Purchase #6	$248.89	12.125%	$279.0679	$279.07	$279.05	$279.10
Purchase #7	$235.31	6.124%	$249.7204	$249.72	$249.70	$249.70
7 purchase totals =	$891.41		$968.6130	$968.61	$968.60	$968.60