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	$223.39	11.286%	$248.6018	$248.60	$248.60	$248.60
Purchase #2	$17.49	11.291%	$19.4648	$19.46	$19.45	$19.50
Purchase #3	$117.85	10.328%	$130.0215	$130.02	$130.00	$130.00
Purchase #4	$103.39	13.414%	$117.2587	$117.26	$117.25	$117.30
Purchase #5	$63.92	13.512%	$72.5569	$72.56	$72.55	$72.60
Purchase #6	$25.61	8.236%	$27.7192	$27.72	$27.70	$27.70
Purchase #7	$102.92	8.569%	$111.7392	$111.74	$111.75	$111.70
7 purchase totals =	$654.57		$727.3621	$727.36	$727.30	$727.40