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	$97.36	8.461%	$105.5976	$105.60	$105.60	$105.60
Purchase #2	$119.59	4.238%	$124.6582	$124.66	$124.65	$124.70
Purchase #3	$136.37	10.150%	$150.2116	$150.21	$150.20	$150.20
Purchase #4	$50.56	13.500%	$57.3856	$57.39	$57.40	$57.40
Purchase #5	$64.93	11.735%	$72.5495	$72.55	$72.55	$72.50
Purchase #6	$11.49	11.450%	$12.8056	$12.81	$12.80	$12.80
Purchase #7	$46.72	4.454%	$48.8009	$48.80	$48.80	$48.80
7 purchase totals =	$527.02		$572.0090	$572.02	$572.00	$572.00