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	$168.49	8.274%	$182.4309	$182.43	$182.45	$182.40
Purchase #2	$132.92	10.119%	$146.3702	$146.37	$146.35	$146.40
Purchase #3	$178.71	11.652%	$199.5333	$199.53	$199.55	$199.50
Purchase #4	$53.49	8.111%	$57.8286	$57.83	$57.85	$57.80
Purchase #5	$32.46	6.702%	$34.6355	$34.64	$34.65	$34.60
Purchase #6	$111.72	10.596%	$123.5579	$123.56	$123.55	$123.60
Purchase #7	$17.34	11.322%	$19.3032	$19.30	$19.30	$19.30
7 purchase totals =	$695.13		$763.6596	$763.66	$763.70	$763.60