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	$64.46	5.725%	$68.1503	$68.15	$68.15	$68.20
Purchase #2	$158.81	11.284%	$176.7301	$176.73	$176.75	$176.70
Purchase #3	$32.25	5.285%	$33.9544	$33.95	$33.95	$34.00
Purchase #4	$180.70	5.653%	$190.915	$190.92	$190.90	$190.90
Purchase #5	$98.41	13.280%	$111.4788	$111.48	$111.50	$111.50
Purchase #6	$152.37	10.651%	$168.5989	$168.60	$168.60	$168.60
Purchase #7	$32.40	13.662%	$36.8265	$36.83	$36.85	$36.80
7 purchase totals =	$719.40		$786.6540	$786.66	$786.70	$786.70