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	$50.62	11.478%	$56.4302	$56.43	$56.45	$56.40
Purchase #2	$167.92	13.536%	$190.6497	$190.65	$190.65	$190.60
Purchase #3	$132.72	7.678%	$142.9102	$142.91	$142.90	$142.90
Purchase #4	$182.46	8.679%	$198.2957	$198.30	$198.30	$198.30
Purchase #5	$80.74	11.298%	$89.862	$89.86	$89.85	$89.90
Purchase #6	$203.68	10.239%	$224.5348	$224.53	$224.55	$224.50
Purchase #7	$110.58	5.280%	$116.4186	$116.42	$116.40	$116.40
7 purchase totals =	$928.72		$1,019.1012	$1,019.10	$1,019.10	$1,019.00