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	$113.65	3.291%	$117.3902	$117.39	$117.40	$117.40
Purchase #2	$172.76	13.554%	$196.1759	$196.18	$196.20	$196.20
Purchase #3	$100.38	12.573%	$113.0008	$113.00	$113.00	$113.00
Purchase #4	$105.42	6.841%	$112.6318	$112.63	$112.65	$112.60
Purchase #5	$64.27	3.660%	$66.6223	$66.62	$66.60	$66.60
Purchase #6	$237.75	5.819%	$251.5847	$251.58	$251.60	$251.60
Purchase #7	$191.29	7.637%	$205.8988	$205.90	$205.90	$205.90
7 purchase totals =	$985.52		$1,063.3045	$1,063.30	$1,063.35	$1,063.30