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	$42.50	10.276%	$46.8673	$46.87	$46.85	$46.90
Purchase #2	$45.70	8.323%	$49.5036	$49.50	$49.50	$49.50
Purchase #3	$169.66	3.419%	$175.4607	$175.46	$175.45	$175.50
Purchase #4	$249.74	13.475%	$283.3925	$283.39	$283.40	$283.40
Purchase #5	$131.71	10.761%	$145.8833	$145.88	$145.90	$145.90
Purchase #6	$104.51	6.487%	$111.2896	$111.29	$111.30	$111.30
Purchase #7	$134.68	11.542%	$150.2248	$150.22	$150.20	$150.20
7 purchase totals =	$878.50		$962.6218	$962.61	$962.60	$962.70