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	$89.45	7.292%	$95.9727	$95.97	$95.95	$96.00
Purchase #2	$74.76	13.873%	$85.1315	$85.13	$85.15	$85.10
Purchase #3	$89.88	11.344%	$100.076	$100.08	$100.10	$100.10
Purchase #4	$145.52	13.103%	$164.5875	$164.59	$164.60	$164.60
Purchase #5	$107.71	13.389%	$122.1313	$122.13	$122.15	$122.10
Purchase #6	$127.37	3.690%	$132.07	$132.07	$132.05	$132.10
Purchase #7	$34.33	7.542%	$36.9192	$36.92	$36.90	$36.90
7 purchase totals =	$669.02		$736.8882	$736.89	$736.90	$736.90