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	$80.75	10.788%	$89.4613	$89.46	$89.45	$89.50
Purchase #2	$82.44	11.630%	$92.0278	$92.03	$92.05	$92.00
Purchase #3	$11.39	11.552%	$12.7058	$12.71	$12.70	$12.70
Purchase #4	$217.29	7.682%	$233.9822	$233.98	$234.00	$234.00
Purchase #5	$145.27	5.658%	$153.4894	$153.49	$153.50	$153.50
Purchase #6	$63.75	3.183%	$65.7792	$65.78	$65.80	$65.80
Purchase #7	$136.44	12.564%	$153.5823	$153.58	$153.60	$153.60
7 purchase totals =	$737.33		$801.0280	$801.03	$801.10	$801.10