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	$104.29	13.753%	$118.633	$118.63	$118.65	$118.60
Purchase #2	$46.68	6.477%	$49.7035	$49.70	$49.70	$49.70
Purchase #3	$122.81	3.773%	$127.4436	$127.44	$127.45	$127.40
Purchase #4	$137.53	4.107%	$143.1784	$143.18	$143.20	$143.20
Purchase #5	$143.31	10.628%	$158.541	$158.54	$158.55	$158.50
Purchase #6	$245.39	13.474%	$278.4538	$278.45	$278.45	$278.50
Purchase #7	$126.39	11.198%	$140.5432	$140.54	$140.55	$140.50
7 purchase totals =	$926.40		$1,016.4965	$1,016.48	$1,016.55	$1,016.40