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	$32.40	12.568%	$36.472	$36.47	$36.45	$36.50
Purchase #2	$59.62	13.416%	$67.6186	$67.62	$67.60	$67.60
Purchase #3	$131.62	10.797%	$145.831	$145.83	$145.85	$145.80
Purchase #4	$225.64	3.299%	$233.0839	$233.08	$233.10	$233.10
Purchase #5	$40.72	12.240%	$45.7041	$45.70	$45.70	$45.70
Purchase #6	$225.50	3.827%	$234.1299	$234.13	$234.15	$234.10
Purchase #7	$85.75	13.196%	$97.0656	$97.07	$97.05	$97.10
7 purchase totals =	$801.25		$859.9051	$859.90	$859.90	$859.90