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	$163.39	3.456%	$169.0368	$169.04	$169.05	$169.00
Purchase #2	$68.68	5.247%	$72.2836	$72.28	$72.30	$72.30
Purchase #3	$120.52	6.547%	$128.4104	$128.41	$128.40	$128.40
Purchase #4	$18.61	13.417%	$21.1069	$21.11	$21.10	$21.10
Purchase #5	$174.78	9.183%	$190.83	$190.83	$190.85	$190.80
Purchase #6	$71.85	13.355%	$81.4456	$81.45	$81.45	$81.40
Purchase #7	$170.75	4.321%	$178.1281	$178.13	$178.15	$178.10
7 purchase totals =	$788.58		$841.2414	$841.25	$841.30	$841.10