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	$44.78	8.434%	$48.5567	$48.56	$48.55	$48.60
Purchase #2	$73.60	11.286%	$81.9065	$81.91	$81.90	$81.90
Purchase #3	$127.71	13.293%	$144.6865	$144.69	$144.70	$144.70
Purchase #4	$21.71	13.291%	$24.5955	$24.60	$24.60	$24.60
Purchase #5	$160.28	5.415%	$168.9592	$168.96	$168.95	$169.00
Purchase #6	$191.95	4.417%	$200.4284	$200.43	$200.45	$200.40
Purchase #7	$107.36	6.442%	$114.2761	$114.28	$114.30	$114.30
7 purchase totals =	$727.39		$783.4089	$783.43	$783.45	$783.50