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	$233.32	10.345%	$257.457	$257.46	$257.45	$257.50
Purchase #2	$151.58	9.848%	$166.5076	$166.51	$166.50	$166.50
Purchase #3	$74.63	11.107%	$82.9192	$82.92	$82.90	$82.90
Purchase #4	$66.42	11.105%	$73.7959	$73.80	$73.80	$73.80
Purchase #5	$11.48	12.112%	$12.8705	$12.87	$12.85	$12.90
Purchase #6	$194.65	5.531%	$205.4161	$205.42	$205.40	$205.40
Purchase #7	$133.47	6.587%	$142.2617	$142.26	$142.25	$142.30
7 purchase totals =	$865.55		$941.2280	$941.24	$941.15	$941.30