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	$58.82	13.643%	$66.8448	$66.84	$66.85	$66.80
Purchase #2	$233.30	3.247%	$240.8753	$240.88	$240.90	$240.90
Purchase #3	$17.89	10.563%	$19.7797	$19.78	$19.80	$19.80
Purchase #4	$100.50	5.371%	$105.8979	$105.90	$105.90	$105.90
Purchase #5	$53.78	4.568%	$56.2367	$56.24	$56.25	$56.20
Purchase #6	$228.72	12.722%	$257.8178	$257.82	$257.80	$257.80
Purchase #7	$54.64	11.811%	$61.0935	$61.09	$61.10	$61.10
7 purchase totals =	$747.65		$808.5457	$808.55	$808.60	$808.50