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	$46.61	9.422%	$51.0016	$51.00	$51.00	$51.00
Purchase #2	$228.46	13.545%	$259.4049	$259.40	$259.40	$259.40
Purchase #3	$117.52	11.552%	$131.0959	$131.10	$131.10	$131.10
Purchase #4	$221.92	5.248%	$233.5664	$233.57	$233.55	$233.60
Purchase #5	$65.96	9.610%	$72.2988	$72.30	$72.30	$72.30
Purchase #6	$97.66	12.732%	$110.0941	$110.09	$110.10	$110.10
Purchase #7	$183.89	4.236%	$191.6796	$191.68	$191.70	$191.70
7 purchase totals =	$962.02		$1,049.1413	$1,049.14	$1,049.15	$1,049.20