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	$106.56	13.193%	$120.6185	$120.62	$120.60	$120.60
Purchase #2	$78.90	10.117%	$86.8823	$86.88	$86.90	$86.90
Purchase #3	$30.28	6.603%	$32.2794	$32.28	$32.30	$32.30
Purchase #4	$64.33	12.852%	$72.5977	$72.60	$72.60	$72.60
Purchase #5	$111.64	4.818%	$117.0188	$117.02	$117.00	$117.00
Purchase #6	$121.80	13.721%	$138.5122	$138.51	$138.50	$138.50
Purchase #7	$145.59	8.504%	$157.971	$157.97	$157.95	$158.00
7 purchase totals =	$659.10		$725.8799	$725.88	$725.85	$725.90