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	$148.79	11.422%	$165.7848	$165.78	$165.80	$165.80
Purchase #2	$50.60	9.253%	$55.282	$55.28	$55.30	$55.30
Purchase #3	$61.39	3.571%	$63.5822	$63.58	$63.60	$63.60
Purchase #4	$221.86	7.585%	$238.6881	$238.69	$238.70	$238.70
Purchase #5	$137.78	4.652%	$144.1895	$144.19	$144.20	$144.20
Purchase #6	$35.66	10.358%	$39.3537	$39.35	$39.35	$39.40
Purchase #7	$34.86	7.656%	$37.5289	$37.53	$37.55	$37.50
7 purchase totals =	$690.94		$744.4092	$744.40	$744.50	$744.50