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	$29.74	11.303%	$33.1015	$33.10	$33.10	$33.10
Purchase #2	$17.28	5.467%	$18.2247	$18.22	$18.20	$18.20
Purchase #3	$228.89	10.104%	$252.017	$252.02	$252.00	$252.00
Purchase #4	$18.81	9.110%	$20.5236	$20.52	$20.50	$20.50
Purchase #5	$172.83	7.326%	$185.4915	$185.49	$185.50	$185.50
Purchase #6	$23.53	6.805%	$25.1312	$25.13	$25.15	$25.10
Purchase #7	$137.60	10.444%	$151.9709	$151.97	$151.95	$152.00
7 purchase totals =	$628.68		$686.4604	$686.45	$686.40	$686.40