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	$96.36	8.510%	$104.5602	$104.56	$104.55	$104.60
Purchase #2	$99.59	5.207%	$104.7757	$104.78	$104.80	$104.80
Purchase #3	$104.37	10.312%	$115.1326	$115.13	$115.15	$115.10
Purchase #4	$127.36	11.724%	$142.2917	$142.29	$142.30	$142.30
Purchase #5	$23.87	6.733%	$25.4772	$25.48	$25.50	$25.50
Purchase #6	$127.86	11.513%	$142.5805	$142.58	$142.60	$142.60
Purchase #7	$220.68	6.754%	$235.5847	$235.58	$235.60	$235.60
7 purchase totals =	$800.09		$870.4026	$870.40	$870.50	$870.50