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	$154.69	13.837%	$176.0945	$176.09	$176.10	$176.10
Purchase #2	$59.94	8.520%	$65.0469	$65.05	$65.05	$65.00
Purchase #3	$39.39	13.462%	$44.6927	$44.69	$44.70	$44.70
Purchase #4	$214.46	6.211%	$227.7801	$227.78	$227.80	$227.80
Purchase #5	$104.32	6.668%	$111.2761	$111.28	$111.30	$111.30
Purchase #6	$82.85	9.363%	$90.6072	$90.61	$90.60	$90.60
Purchase #7	$30.66	4.432%	$32.0189	$32.02	$32.00	$32.00
7 purchase totals =	$686.31		$747.5164	$747.52	$747.55	$747.50