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	$114.61	11.142%	$127.3798	$127.38	$127.40	$127.40
Purchase #2	$48.57	11.233%	$54.0259	$54.03	$54.05	$54.00
Purchase #3	$181.40	13.152%	$205.2577	$205.26	$205.25	$205.30
Purchase #4	$45.95	5.377%	$48.4207	$48.42	$48.40	$48.40
Purchase #5	$246.46	8.550%	$267.5323	$267.53	$267.55	$267.50
Purchase #6	$229.94	4.269%	$239.7561	$239.76	$239.75	$239.80
Purchase #7	$150.72	10.168%	$166.0452	$166.05	$166.05	$166.00
7 purchase totals =	$1,017.65		$1,108.4177	$1,108.43	$1,108.45	$1,108.40