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	$10.76	6.258%	$11.4334	$11.43	$11.45	$11.40
Purchase #2	$124.33	12.190%	$139.4858	$139.49	$139.50	$139.50
Purchase #3	$27.68	5.158%	$29.1077	$29.11	$29.10	$29.10
Purchase #4	$195.94	13.453%	$222.2998	$222.30	$222.30	$222.30
Purchase #5	$42.80	12.364%	$48.0918	$48.09	$48.10	$48.10
Purchase #6	$166.72	6.826%	$178.1003	$178.10	$178.10	$178.10
Purchase #7	$140.42	13.191%	$158.9428	$158.94	$158.95	$158.90
7 purchase totals =	$708.65		$787.4616	$787.46	$787.50	$787.40