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	$144.98	11.737%	$161.9963	$162.00	$162.00	$162.00
Purchase #2	$40.89	3.522%	$42.3301	$42.33	$42.35	$42.30
Purchase #3	$111.58	10.459%	$123.2502	$123.25	$123.25	$123.30
Purchase #4	$230.96	9.667%	$253.2869	$253.29	$253.30	$253.30
Purchase #5	$184.83	4.304%	$192.7851	$192.79	$192.80	$192.80
Purchase #6	$214.44	7.451%	$230.4179	$230.42	$230.40	$230.40
Purchase #7	$9.78	5.205%	$10.289	$10.29	$10.30	$10.30
7 purchase totals =	$937.46		$1,014.3555	$1,014.37	$1,014.40	$1,014.40