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	$27.82	5.289%	$29.2914	$29.29	$29.30	$29.30
Purchase #2	$187.79	9.140%	$204.954	$204.95	$204.95	$205.00
Purchase #3	$89.89	11.356%	$100.0979	$100.10	$100.10	$100.10
Purchase #4	$214.88	5.440%	$226.5695	$226.57	$226.55	$226.60
Purchase #5	$48.98	10.713%	$54.2272	$54.23	$54.25	$54.20
Purchase #6	$126.40	6.467%	$134.5743	$134.57	$134.55	$134.60
Purchase #7	$237.35	12.433%	$266.8597	$266.86	$266.85	$266.90
7 purchase totals =	$933.11		$1,016.5740	$1,016.57	$1,016.55	$1,016.70