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	$158.43	9.126%	$172.8883	$172.89	$172.90	$172.90
Purchase #2	$65.43	4.872%	$68.6177	$68.62	$68.60	$68.60
Purchase #3	$224.28	5.777%	$237.2367	$237.24	$237.25	$237.20
Purchase #4	$92.77	3.606%	$96.1153	$96.12	$96.10	$96.10
Purchase #5	$44.78	5.329%	$47.1663	$47.17	$47.15	$47.20
Purchase #6	$37.37	11.414%	$41.6354	$41.64	$41.65	$41.60
Purchase #7	$92.50	8.667%	$100.517	$100.52	$100.50	$100.50
7 purchase totals =	$715.56		$764.1767	$764.20	$764.15	$764.10