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	$137.29	8.378%	$148.7922	$148.79	$148.80	$148.80
Purchase #2	$192.39	8.644%	$209.0202	$209.02	$209.00	$209.00
Purchase #3	$105.41	12.733%	$118.8319	$118.83	$118.85	$118.80
Purchase #4	$57.44	3.338%	$59.3573	$59.36	$59.35	$59.40
Purchase #5	$128.73	3.712%	$133.5085	$133.51	$133.50	$133.50
Purchase #6	$230.43	13.840%	$262.3215	$262.32	$262.30	$262.30
Purchase #7	$95.58	6.350%	$101.6493	$101.65	$101.65	$101.60
7 purchase totals =	$947.27		$1,033.4809	$1,033.48	$1,033.45	$1,033.40