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	$89.76	5.410%	$94.616	$94.62	$94.60	$94.60
Purchase #2	$60.88	10.477%	$67.2584	$67.26	$67.25	$67.30
Purchase #3	$60.73	10.386%	$67.0374	$67.04	$67.05	$67.00
Purchase #4	$164.32	5.545%	$173.4315	$173.43	$173.45	$173.40
Purchase #5	$137.87	4.710%	$144.3637	$144.36	$144.35	$144.40
Purchase #6	$95.77	10.466%	$105.7933	$105.79	$105.80	$105.80
Purchase #7	$128.64	5.540%	$135.7667	$135.77	$135.75	$135.80
7 purchase totals =	$737.97		$788.2670	$788.27	$788.25	$788.30