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	$168.52	13.257%	$190.8607	$190.86	$190.85	$190.90
Purchase #2	$232.50	10.136%	$256.0662	$256.07	$256.05	$256.10
Purchase #3	$116.72	9.521%	$127.8329	$127.83	$127.85	$127.80
Purchase #4	$159.43	9.229%	$174.1438	$174.14	$174.15	$174.10
Purchase #5	$121.32	7.155%	$130.0004	$130.00	$130.00	$130.00
Purchase #6	$24.33	3.761%	$25.2451	$25.25	$25.25	$25.20
Purchase #7	$90.68	5.733%	$95.8787	$95.88	$95.90	$95.90
7 purchase totals =	$913.50		$1,000.0278	$1,000.03	$1,000.05	$1,000.00