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	$51.45	10.521%	$56.8631	$56.86	$56.85	$56.90
Purchase #2	$41.68	11.797%	$46.597	$46.60	$46.60	$46.60
Purchase #3	$101.76	9.109%	$111.0293	$111.03	$111.05	$111.00
Purchase #4	$92.62	4.506%	$96.7935	$96.79	$96.80	$96.80
Purchase #5	$249.46	6.843%	$266.5305	$266.53	$266.55	$266.50
Purchase #6	$109.32	9.331%	$119.5206	$119.52	$119.50	$119.50
Purchase #7	$120.55	12.866%	$136.06	$136.06	$136.05	$136.10
7 purchase totals =	$766.84		$833.3940	$833.39	$833.40	$833.40