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	$200.27	11.707%	$223.7156	$223.72	$223.70	$223.70
Purchase #2	$100.97	4.406%	$105.4187	$105.42	$105.40	$105.40
Purchase #3	$158.40	8.636%	$172.0794	$172.08	$172.10	$172.10
Purchase #4	$117.80	12.653%	$132.7052	$132.71	$132.70	$132.70
Purchase #5	$77.65	6.374%	$82.5994	$82.60	$82.60	$82.60
Purchase #6	$130.60	8.222%	$141.3379	$141.34	$141.35	$141.30
Purchase #7	$246.74	7.481%	$265.1986	$265.20	$265.20	$265.20
7 purchase totals =	$1,032.43		$1,123.0548	$1,123.07	$1,123.05	$1,123.00