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	$249.64	3.805%	$259.1388	$259.14	$259.15	$259.10
Purchase #2	$92.86	13.838%	$105.71	$105.71	$105.70	$105.70
Purchase #3	$198.42	8.585%	$215.4544	$215.45	$215.45	$215.50
Purchase #4	$38.87	12.129%	$43.5845	$43.58	$43.60	$43.60
Purchase #5	$193.93	13.678%	$220.4557	$220.46	$220.45	$220.50
Purchase #6	$172.49	13.814%	$196.3178	$196.32	$196.30	$196.30
Purchase #7	$138.34	12.664%	$155.8594	$155.86	$155.85	$155.90
7 purchase totals =	$1,084.55		$1,196.5206	$1,196.52	$1,196.50	$1,196.60