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	$30.32	11.400%	$33.7765	$33.78	$33.80	$33.80
Purchase #2	$94.49	9.536%	$103.5006	$103.50	$103.50	$103.50
Purchase #3	$60.83	9.523%	$66.6228	$66.62	$66.60	$66.60
Purchase #4	$105.95	5.534%	$111.8133	$111.81	$111.80	$111.80
Purchase #5	$19.83	4.653%	$20.7527	$20.75	$20.75	$20.80
Purchase #6	$137.52	3.790%	$142.732	$142.73	$142.75	$142.70
Purchase #7	$243.77	9.848%	$267.7765	$267.78	$267.80	$267.80
7 purchase totals =	$692.71		$746.9744	$746.97	$747.00	$747.00