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	$65.50	7.871%	$70.6555	$70.66	$70.65	$70.70
Purchase #2	$100.80	6.531%	$107.3832	$107.38	$107.40	$107.40
Purchase #3	$39.56	4.594%	$41.3774	$41.38	$41.40	$41.40
Purchase #4	$129.35	13.117%	$146.3168	$146.32	$146.30	$146.30
Purchase #5	$57.63	6.630%	$61.4509	$61.45	$61.45	$61.50
Purchase #6	$98.34	10.820%	$108.9804	$108.98	$109.00	$109.00
Purchase #7	$184.52	6.538%	$196.5839	$196.58	$196.60	$196.60
7 purchase totals =	$675.70		$732.7481	$732.75	$732.80	$732.90