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	$157.59	11.643%	$175.9382	$175.94	$175.95	$175.90
Purchase #2	$86.49	6.666%	$92.2554	$92.26	$92.25	$92.30
Purchase #3	$97.72	13.651%	$111.0598	$111.06	$111.05	$111.10
Purchase #4	$172.42	13.812%	$196.2347	$196.23	$196.25	$196.20
Purchase #5	$63.47	10.551%	$70.1667	$70.17	$70.15	$70.20
Purchase #6	$96.64	8.248%	$104.6109	$104.61	$104.60	$104.60
Purchase #7	$220.86	3.227%	$227.9872	$227.99	$228.00	$228.00
7 purchase totals =	$895.19		$978.2529	$978.26	$978.25	$978.30