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	$34.64	8.615%	$37.6242	$37.62	$37.60	$37.60
Purchase #2	$81.89	5.729%	$86.5815	$86.58	$86.60	$86.60
Purchase #3	$38.72	9.551%	$42.4181	$42.42	$42.40	$42.40
Purchase #4	$24.32	13.573%	$27.621	$27.62	$27.60	$27.60
Purchase #5	$138.88	10.402%	$153.3263	$153.33	$153.35	$153.30
Purchase #6	$222.52	13.337%	$252.1975	$252.20	$252.20	$252.20
Purchase #7	$121.30	4.490%	$126.7464	$126.75	$126.75	$126.70
7 purchase totals =	$662.27		$726.5150	$726.52	$726.50	$726.40