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	$247.42	6.822%	$264.299	$264.30	$264.30	$264.30
Purchase #2	$113.79	8.766%	$123.7648	$123.76	$123.75	$123.80
Purchase #3	$95.83	5.339%	$100.9464	$100.95	$100.95	$100.90
Purchase #4	$137.83	5.212%	$145.0137	$145.01	$145.00	$145.00
Purchase #5	$10.63	4.814%	$11.1417	$11.14	$11.15	$11.10
Purchase #6	$163.59	9.133%	$178.5307	$178.53	$178.55	$178.50
Purchase #7	$67.30	8.606%	$73.0918	$73.09	$73.10	$73.10
7 purchase totals =	$836.39		$896.7881	$896.78	$896.80	$896.70