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	$6.26	13.102%	$7.0802	$7.08	$7.10	$7.10
Purchase #2	$9.71	7.687%	$10.4564	$10.46	$10.45	$10.50
Purchase #3	$81.62	4.626%	$85.3957	$85.40	$85.40	$85.40
Purchase #4	$21.43	12.355%	$24.0777	$24.08	$24.10	$24.10
Purchase #5	$139.94	10.869%	$155.1501	$155.15	$155.15	$155.20
Purchase #6	$131.42	13.130%	$148.6754	$148.68	$148.70	$148.70
Purchase #7	$86.86	4.743%	$90.9798	$90.98	$91.00	$91.00
7 purchase totals =	$477.24		$521.8153	$521.83	$521.90	$522.00