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	$47.87	6.750%	$51.1012	$51.10	$51.10	$51.10
Purchase #2	$215.39	4.262%	$224.5699	$224.57	$224.55	$224.60
Purchase #3	$56.34	5.613%	$59.5024	$59.50	$59.50	$59.50
Purchase #4	$73.29	4.290%	$76.4341	$76.43	$76.45	$76.40
Purchase #5	$119.72	5.371%	$126.1502	$126.15	$126.15	$126.20
Purchase #6	$57.88	6.406%	$61.5878	$61.59	$61.60	$61.60
Purchase #7	$106.59	9.106%	$116.2961	$116.30	$116.30	$116.30
7 purchase totals =	$677.08		$715.6417	$715.64	$715.65	$715.70