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	$183.72	3.761%	$190.6297	$190.63	$190.65	$190.60
Purchase #2	$237.92	8.730%	$258.6904	$258.69	$258.70	$258.70
Purchase #3	$89.45	4.845%	$93.7839	$93.78	$93.80	$93.80
Purchase #4	$103.73	7.874%	$111.8977	$111.90	$111.90	$111.90
Purchase #5	$148.97	5.305%	$156.8729	$156.87	$156.85	$156.90
Purchase #6	$33.99	8.493%	$36.8768	$36.88	$36.90	$36.90
Purchase #7	$41.47	11.691%	$46.3183	$46.32	$46.30	$46.30
7 purchase totals =	$839.25		$895.0697	$895.07	$895.10	$895.10