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	$43.93	13.524%	$49.8711	$49.87	$49.85	$49.90
Purchase #2	$214.97	7.613%	$231.3357	$231.34	$231.35	$231.30
Purchase #3	$16.84	13.527%	$19.1179	$19.12	$19.10	$19.10
Purchase #4	$99.34	12.117%	$111.377	$111.38	$111.40	$111.40
Purchase #5	$160.34	10.212%	$176.7139	$176.71	$176.70	$176.70
Purchase #6	$155.64	11.804%	$174.0117	$174.01	$174.00	$174.00
Purchase #7	$185.95	7.618%	$200.1157	$200.12	$200.10	$200.10
7 purchase totals =	$877.01		$962.5430	$962.55	$962.50	$962.50