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	$57.55	8.566%	$62.4797	$62.48	$62.50	$62.50
Purchase #2	$55.93	12.222%	$62.7658	$62.77	$62.75	$62.80
Purchase #3	$121.67	10.553%	$134.5098	$134.51	$134.50	$134.50
Purchase #4	$34.89	11.772%	$38.9973	$39.00	$39.00	$39.00
Purchase #5	$131.56	10.513%	$145.3909	$145.39	$145.40	$145.40
Purchase #6	$151.42	8.371%	$164.0954	$164.10	$164.10	$164.10
Purchase #7	$165.94	4.772%	$173.8587	$173.86	$173.85	$173.90
7 purchase totals =	$718.96		$782.0976	$782.11	$782.10	$782.20