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	$41.87	7.825%	$45.1463	$45.15	$45.15	$45.10
Purchase #2	$59.85	3.209%	$61.7706	$61.77	$61.75	$61.80
Purchase #3	$156.51	7.736%	$168.6176	$168.62	$168.60	$168.60
Purchase #4	$32.75	6.295%	$34.8116	$34.81	$34.80	$34.80
Purchase #5	$226.51	11.516%	$252.5949	$252.59	$252.60	$252.60
Purchase #6	$16.89	3.799%	$17.5317	$17.53	$17.55	$17.50
Purchase #7	$62.92	11.256%	$70.0023	$70.00	$70.00	$70.00
7 purchase totals =	$597.30		$650.4750	$650.47	$650.45	$650.40