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	$215.64	6.454%	$229.5574	$229.56	$229.55	$229.60
Purchase #2	$102.43	8.538%	$111.1755	$111.18	$111.20	$111.20
Purchase #3	$10.49	5.639%	$11.0815	$11.08	$11.10	$11.10
Purchase #4	$137.94	5.301%	$145.2522	$145.25	$145.25	$145.30
Purchase #5	$228.54	10.781%	$253.1789	$253.18	$253.20	$253.20
Purchase #6	$45.67	7.291%	$48.9998	$49.00	$49.00	$49.00
Purchase #7	$171.61	4.188%	$178.797	$178.80	$178.80	$178.80
7 purchase totals =	$912.32		$978.0423	$978.05	$978.10	$978.20