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	$54.37	4.291%	$56.703	$56.70	$56.70	$56.70
Purchase #2	$55.94	5.520%	$59.0279	$59.03	$59.05	$59.00
Purchase #3	$101.52	9.427%	$111.0903	$111.09	$111.10	$111.10
Purchase #4	$125.55	4.678%	$131.4232	$131.42	$131.40	$131.40
Purchase #5	$246.50	11.460%	$274.7489	$274.75	$274.75	$274.70
Purchase #6	$224.87	12.344%	$252.628	$252.63	$252.65	$252.60
Purchase #7	$123.95	6.291%	$131.7477	$131.75	$131.75	$131.70
7 purchase totals =	$932.70		$1,017.3690	$1,017.37	$1,017.40	$1,017.20