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	$70.87	10.631%	$78.4042	$78.40	$78.40	$78.40
Purchase #2	$208.71	9.291%	$228.1012	$228.10	$228.10	$228.10
Purchase #3	$128.60	6.611%	$137.1017	$137.10	$137.10	$137.10
Purchase #4	$180.73	5.509%	$190.6864	$190.69	$190.70	$190.70
Purchase #5	$243.35	5.294%	$256.2329	$256.23	$256.25	$256.20
Purchase #6	$181.67	6.365%	$193.2333	$193.23	$193.25	$193.20
Purchase #7	$18.25	10.494%	$20.1652	$20.17	$20.15	$20.20
7 purchase totals =	$1,032.18		$1,103.9249	$1,103.92	$1,103.95	$1,103.90