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	$101.36	12.852%	$114.3868	$114.39	$114.40	$114.40
Purchase #2	$47.32	13.661%	$53.7844	$53.78	$53.80	$53.80
Purchase #3	$132.39	10.745%	$146.6153	$146.62	$146.60	$146.60
Purchase #4	$66.96	13.873%	$76.2494	$76.25	$76.25	$76.20
Purchase #5	$37.31	6.715%	$39.8154	$39.82	$39.80	$39.80
Purchase #6	$205.49	13.456%	$233.1407	$233.14	$233.15	$233.10
Purchase #7	$102.86	10.376%	$113.5328	$113.53	$113.55	$113.50
7 purchase totals =	$693.69		$777.5248	$777.53	$777.55	$777.40