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	$29.25	12.551%	$32.9212	$32.92	$32.90	$32.90
Purchase #2	$20.25	6.269%	$21.5195	$21.52	$21.50	$21.50
Purchase #3	$9.95	4.440%	$10.3918	$10.39	$10.40	$10.40
Purchase #4	$163.29	13.335%	$185.0647	$185.06	$185.05	$185.10
Purchase #5	$226.84	5.351%	$238.9782	$238.98	$239.00	$239.00
Purchase #6	$81.42	7.315%	$87.3759	$87.38	$87.40	$87.40
Purchase #7	$233.96	9.328%	$255.7838	$255.78	$255.80	$255.80
7 purchase totals =	$764.96		$832.0351	$832.03	$832.05	$832.10