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	$102.96	12.693%	$116.0287	$116.03	$116.05	$116.00
Purchase #2	$215.28	11.164%	$239.3139	$239.31	$239.30	$239.30
Purchase #3	$125.41	7.332%	$134.6051	$134.61	$134.60	$134.60
Purchase #4	$86.72	4.274%	$90.4264	$90.43	$90.45	$90.40
Purchase #5	$186.45	5.489%	$196.6842	$196.68	$196.70	$196.70
Purchase #6	$122.28	3.103%	$126.0743	$126.07	$126.05	$126.10
Purchase #7	$57.38	11.384%	$63.9121	$63.91	$63.90	$63.90
7 purchase totals =	$896.48		$967.0447	$967.04	$967.05	$967.00