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	$182.82	6.446%	$194.6046	$194.60	$194.60	$194.60
Purchase #2	$126.55	10.141%	$139.3834	$139.38	$139.40	$139.40
Purchase #3	$138.76	9.833%	$152.4043	$152.40	$152.40	$152.40
Purchase #4	$116.60	9.504%	$127.6817	$127.68	$127.70	$127.70
Purchase #5	$11.68	3.140%	$12.0468	$12.05	$12.05	$12.00
Purchase #6	$102.98	8.338%	$111.5665	$111.57	$111.55	$111.60
Purchase #7	$121.51	4.107%	$126.5004	$126.50	$126.50	$126.50
7 purchase totals =	$800.90		$864.1877	$864.18	$864.20	$864.20