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	$175.82	6.514%	$187.2729	$187.27	$187.25	$187.30
Purchase #2	$177.45	12.733%	$200.0447	$200.04	$200.05	$200.00
Purchase #3	$10.77	4.319%	$11.2352	$11.24	$11.25	$11.20
Purchase #4	$233.64	9.250%	$255.2517	$255.25	$255.25	$255.30
Purchase #5	$74.44	4.178%	$77.5501	$77.55	$77.55	$77.60
Purchase #6	$238.59	6.213%	$253.4136	$253.41	$253.40	$253.40
Purchase #7	$51.55	8.186%	$55.7699	$55.77	$55.75	$55.80
7 purchase totals =	$962.26		$1,040.5381	$1,040.53	$1,040.50	$1,040.60