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	$126.71	13.509%	$143.8273	$143.83	$143.85	$143.80
Purchase #2	$249.49	12.263%	$280.085	$280.09	$280.10	$280.10
Purchase #3	$26.96	4.861%	$28.2705	$28.27	$28.25	$28.30
Purchase #4	$169.35	11.664%	$189.103	$189.10	$189.10	$189.10
Purchase #5	$59.87	13.422%	$67.9058	$67.91	$67.90	$67.90
Purchase #6	$192.80	9.109%	$210.3622	$210.36	$210.35	$210.40
Purchase #7	$143.40	10.534%	$158.5058	$158.51	$158.50	$158.50
7 purchase totals =	$968.58		$1,078.0596	$1,078.07	$1,078.05	$1,078.10