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	$148.32	11.815%	$165.844	$165.84	$165.85	$165.80
Purchase #2	$177.89	12.536%	$200.1903	$200.19	$200.20	$200.20
Purchase #3	$118.75	6.509%	$126.4794	$126.48	$126.50	$126.50
Purchase #4	$240.72	3.791%	$249.8457	$249.85	$249.85	$249.80
Purchase #5	$206.85	3.783%	$214.6751	$214.68	$214.70	$214.70
Purchase #6	$181.61	8.449%	$196.9542	$196.95	$196.95	$197.00
Purchase #7	$12.58	9.827%	$13.8162	$13.82	$13.80	$13.80
7 purchase totals =	$1,086.72		$1,167.8049	$1,167.81	$1,167.85	$1,167.80