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	$186.59	4.124%	$194.285	$194.29	$194.30	$194.30
Purchase #2	$163.40	10.386%	$180.3707	$180.37	$180.35	$180.40
Purchase #3	$227.39	12.552%	$255.932	$255.93	$255.95	$255.90
Purchase #4	$169.25	4.733%	$177.2606	$177.26	$177.25	$177.30
Purchase #5	$57.83	3.464%	$59.8332	$59.83	$59.85	$59.80
Purchase #6	$156.30	11.219%	$173.8353	$173.84	$173.85	$173.80
Purchase #7	$122.87	11.856%	$137.4375	$137.44	$137.45	$137.40
7 purchase totals =	$1,083.63		$1,178.9543	$1,178.96	$1,179.00	$1,178.90