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	$215.83	13.733%	$245.4699	$245.47	$245.45	$245.50
Purchase #2	$238.38	8.585%	$258.8449	$258.84	$258.85	$258.80
Purchase #3	$153.61	5.225%	$161.6361	$161.64	$161.65	$161.60
Purchase #4	$49.77	12.451%	$55.9669	$55.97	$55.95	$56.00
Purchase #5	$18.77	4.217%	$19.5615	$19.56	$19.55	$19.60
Purchase #6	$175.67	3.305%	$181.4759	$181.48	$181.50	$181.50
Purchase #7	$110.79	11.513%	$123.5453	$123.55	$123.55	$123.50
7 purchase totals =	$962.82		$1,046.5005	$1,046.51	$1,046.50	$1,046.50