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	$126.62	11.830%	$141.5991	$141.60	$141.60	$141.60
Purchase #2	$56.50	10.528%	$62.4483	$62.45	$62.45	$62.40
Purchase #3	$117.80	11.530%	$131.3823	$131.38	$131.40	$131.40
Purchase #4	$46.76	12.801%	$52.7457	$52.75	$52.75	$52.70
Purchase #5	$53.94	4.735%	$56.4941	$56.49	$56.50	$56.50
Purchase #6	$68.89	7.323%	$73.9348	$73.93	$73.95	$73.90
Purchase #7	$17.58	5.348%	$18.5202	$18.52	$18.50	$18.50
7 purchase totals =	$488.09		$537.1245	$537.12	$537.15	$537.00