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	$106.32	5.279%	$111.9326	$111.93	$111.95	$111.90
Purchase #2	$152.93	8.587%	$166.0621	$166.06	$166.05	$166.10
Purchase #3	$232.70	13.215%	$263.4513	$263.45	$263.45	$263.50
Purchase #4	$95.66	5.670%	$101.0839	$101.08	$101.10	$101.10
Purchase #5	$100.60	3.149%	$103.7679	$103.77	$103.75	$103.80
Purchase #6	$11.86	10.825%	$13.1438	$13.14	$13.15	$13.10
Purchase #7	$26.30	13.227%	$29.7787	$29.78	$29.80	$29.80
7 purchase totals =	$726.37		$789.2203	$789.21	$789.25	$789.30