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	$106.94	5.572%	$112.8987	$112.90	$112.90	$112.90
Purchase #2	$39.88	8.872%	$43.4182	$43.42	$43.40	$43.40
Purchase #3	$162.45	6.269%	$172.634	$172.63	$172.65	$172.60
Purchase #4	$153.87	12.728%	$173.4546	$173.45	$173.45	$173.50
Purchase #5	$175.89	5.510%	$185.5815	$185.58	$185.60	$185.60
Purchase #6	$10.86	3.390%	$11.2282	$11.23	$11.25	$11.20
Purchase #7	$245.43	4.865%	$257.3702	$257.37	$257.35	$257.40
7 purchase totals =	$895.32		$956.5854	$956.58	$956.60	$956.60