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	$31.40	9.628%	$34.4232	$34.42	$34.40	$34.40
Purchase #2	$18.33	7.822%	$19.7638	$19.76	$19.75	$19.80
Purchase #3	$36.83	7.482%	$39.5856	$39.59	$39.60	$39.60
Purchase #4	$62.45	4.550%	$65.2915	$65.29	$65.30	$65.30
Purchase #5	$180.66	8.789%	$196.5382	$196.54	$196.55	$196.50
Purchase #6	$225.25	10.850%	$249.6896	$249.69	$249.70	$249.70
Purchase #7	$133.78	5.547%	$141.2008	$141.20	$141.20	$141.20
7 purchase totals =	$688.70		$746.4927	$746.49	$746.50	$746.50