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	$242.87	9.733%	$266.5085	$266.51	$266.50	$266.50
Purchase #2	$65.34	8.659%	$70.9978	$71.00	$71.00	$71.00
Purchase #3	$250.89	11.253%	$279.1227	$279.12	$279.10	$279.10
Purchase #4	$9.83	7.725%	$10.5894	$10.59	$10.60	$10.60
Purchase #5	$38.33	7.482%	$41.1979	$41.20	$41.20	$41.20
Purchase #6	$225.49	4.423%	$235.4634	$235.46	$235.45	$235.50
Purchase #7	$89.51	8.591%	$97.1998	$97.20	$97.20	$97.20
7 purchase totals =	$922.26		$1,001.0795	$1,001.08	$1,001.05	$1,001.10