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	$76.38	11.779%	$85.3768	$85.38	$85.40	$85.40
Purchase #2	$82.68	3.708%	$85.7458	$85.75	$85.75	$85.70
Purchase #3	$48.74	4.659%	$51.0108	$51.01	$51.00	$51.00
Purchase #4	$86.85	6.714%	$92.6811	$92.68	$92.70	$92.70
Purchase #5	$134.52	10.463%	$148.5948	$148.59	$148.60	$148.60
Purchase #6	$211.73	7.839%	$228.3275	$228.33	$228.35	$228.30
Purchase #7	$24.41	12.321%	$27.4176	$27.42	$27.40	$27.40
7 purchase totals =	$665.31		$719.1544	$719.16	$719.20	$719.10