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	$48.84	10.822%	$54.1255	$54.13	$54.15	$54.10
Purchase #2	$95.98	4.706%	$100.4968	$100.50	$100.50	$100.50
Purchase #3	$37.79	13.279%	$42.8081	$42.81	$42.80	$42.80
Purchase #4	$224.51	3.852%	$233.1581	$233.16	$233.15	$233.20
Purchase #5	$145.96	4.191%	$152.0772	$152.08	$152.10	$152.10
Purchase #6	$159.64	7.793%	$172.0807	$172.08	$172.10	$172.10
Purchase #7	$14.39	9.293%	$15.7273	$15.73	$15.75	$15.70
7 purchase totals =	$727.11		$770.4737	$770.49	$770.55	$770.50