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	$65.62	10.833%	$72.7286	$72.73	$72.75	$72.70
Purchase #2	$144.86	9.622%	$158.7984	$158.80	$158.80	$158.80
Purchase #3	$210.93	6.408%	$224.4464	$224.45	$224.45	$224.40
Purchase #4	$77.55	13.587%	$88.0867	$88.09	$88.10	$88.10
Purchase #5	$33.69	12.224%	$37.8083	$37.81	$37.80	$37.80
Purchase #6	$149.52	4.369%	$156.0525	$156.05	$156.05	$156.10
Purchase #7	$34.64	8.177%	$37.4725	$37.47	$37.45	$37.50
7 purchase totals =	$716.81		$775.3934	$775.40	$775.40	$775.40