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	$229.89	4.604%	$240.4741	$240.47	$240.45	$240.50
Purchase #2	$15.51	13.466%	$17.5986	$17.60	$17.60	$17.60
Purchase #3	$183.88	3.520%	$190.3526	$190.35	$190.35	$190.40
Purchase #4	$51.37	13.531%	$58.3209	$58.32	$58.30	$58.30
Purchase #5	$110.35	8.614%	$119.8555	$119.86	$119.85	$119.90
Purchase #6	$120.68	5.143%	$126.8866	$126.89	$126.90	$126.90
Purchase #7	$221.91	5.230%	$233.5159	$233.52	$233.50	$233.50
7 purchase totals =	$933.59		$987.0042	$987.01	$986.95	$987.10