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	$104.71	10.766%	$115.9831	$115.98	$116.00	$116.00
Purchase #2	$9.30	8.274%	$10.0695	$10.07	$10.05	$10.10
Purchase #3	$94.54	6.779%	$100.9489	$100.95	$100.95	$100.90
Purchase #4	$233.59	6.813%	$249.5045	$249.50	$249.50	$249.50
Purchase #5	$122.68	7.451%	$131.8209	$131.82	$131.80	$131.80
Purchase #6	$19.90	7.796%	$21.4514	$21.45	$21.45	$21.50
Purchase #7	$183.52	4.295%	$191.4022	$191.40	$191.40	$191.40
7 purchase totals =	$768.24		$821.1805	$821.17	$821.15	$821.20