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	$38.38	8.805%	$41.7594	$41.76	$41.75	$41.80
Purchase #2	$151.81	13.480%	$172.274	$172.27	$172.25	$172.30
Purchase #3	$60.46	9.491%	$66.1983	$66.20	$66.20	$66.20
Purchase #4	$86.52	5.156%	$90.981	$90.98	$91.00	$91.00
Purchase #5	$167.78	6.439%	$178.5834	$178.58	$178.60	$178.60
Purchase #6	$37.60	7.240%	$40.3222	$40.32	$40.30	$40.30
Purchase #7	$101.66	3.404%	$105.1205	$105.12	$105.10	$105.10
7 purchase totals =	$644.21		$695.2388	$695.23	$695.20	$695.30