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	$126.84	11.591%	$141.542	$141.54	$141.55	$141.50
Purchase #2	$38.58	6.482%	$41.0808	$41.08	$41.10	$41.10
Purchase #3	$100.77	8.791%	$109.6287	$109.63	$109.65	$109.60
Purchase #4	$92.39	8.661%	$100.3919	$100.39	$100.40	$100.40
Purchase #5	$145.92	4.268%	$152.1479	$152.15	$152.15	$152.10
Purchase #6	$220.98	13.120%	$249.9726	$249.97	$249.95	$250.00
Purchase #7	$193.53	6.264%	$205.6527	$205.65	$205.65	$205.70
7 purchase totals =	$919.01		$1,000.4166	$1,000.41	$1,000.45	$1,000.40