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	$161.70	10.553%	$178.7642	$178.76	$178.75	$178.80
Purchase #2	$107.54	3.339%	$111.1308	$111.13	$111.15	$111.10
Purchase #3	$219.48	6.224%	$233.1404	$233.14	$233.15	$233.10
Purchase #4	$152.73	3.768%	$158.4849	$158.48	$158.50	$158.50
Purchase #5	$17.64	9.789%	$19.3668	$19.37	$19.35	$19.40
Purchase #6	$43.89	12.661%	$49.4469	$49.45	$49.45	$49.40
Purchase #7	$5.77	4.866%	$6.0508	$6.05	$6.05	$6.10
7 purchase totals =	$708.75		$756.3848	$756.38	$756.40	$756.40