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	$79.58	7.318%	$85.4037	$85.40	$85.40	$85.40
Purchase #2	$137.84	7.422%	$148.0705	$148.07	$148.05	$148.10
Purchase #3	$100.78	4.683%	$105.4995	$105.50	$105.50	$105.50
Purchase #4	$13.99	13.760%	$15.915	$15.92	$15.90	$15.90
Purchase #5	$167.41	11.733%	$187.0522	$187.05	$187.05	$187.10
Purchase #6	$102.30	10.573%	$113.1162	$113.12	$113.10	$113.10
Purchase #7	$141.96	6.426%	$151.0823	$151.08	$151.10	$151.10
7 purchase totals =	$743.86		$806.1394	$806.14	$806.10	$806.20