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	$172.29	11.610%	$192.2929	$192.29	$192.30	$192.30
Purchase #2	$137.58	5.573%	$145.2473	$145.25	$145.25	$145.20
Purchase #3	$62.72	4.413%	$65.4878	$65.49	$65.50	$65.50
Purchase #4	$173.31	4.236%	$180.6514	$180.65	$180.65	$180.70
Purchase #5	$232.61	9.867%	$255.5616	$255.56	$255.55	$255.60
Purchase #6	$10.99	7.737%	$11.8403	$11.84	$11.85	$11.80
Purchase #7	$99.67	5.386%	$105.0382	$105.04	$105.05	$105.00
7 purchase totals =	$889.17		$956.1195	$956.12	$956.15	$956.10