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	$159.39	5.439%	$168.0592	$168.06	$168.05	$168.10
Purchase #2	$193.87	9.135%	$211.58	$211.58	$211.60	$211.60
Purchase #3	$61.97	6.422%	$65.9497	$65.95	$65.95	$65.90
Purchase #4	$165.78	7.419%	$178.0792	$178.08	$178.10	$178.10
Purchase #5	$250.51	13.603%	$284.5869	$284.59	$284.60	$284.60
Purchase #6	$26.94	5.686%	$28.4718	$28.47	$28.45	$28.50
Purchase #7	$99.76	4.798%	$104.5465	$104.55	$104.55	$104.50
7 purchase totals =	$958.22		$1,041.2733	$1,041.28	$1,041.30	$1,041.30