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	$179.62	8.841%	$195.5002	$195.50	$195.50	$195.50
Purchase #2	$157.79	13.687%	$179.3867	$179.39	$179.40	$179.40
Purchase #3	$167.80	12.247%	$188.3505	$188.35	$188.35	$188.40
Purchase #4	$112.65	4.629%	$117.8646	$117.86	$117.85	$117.90
Purchase #5	$158.59	4.712%	$166.0628	$166.06	$166.05	$166.10
Purchase #6	$231.57	10.422%	$255.7042	$255.70	$255.70	$255.70
Purchase #7	$70.56	9.584%	$77.3225	$77.32	$77.30	$77.30
7 purchase totals =	$1,078.58		$1,180.1915	$1,180.18	$1,180.15	$1,180.30