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	$230.77	11.866%	$258.1532	$258.15	$258.15	$258.20
Purchase #2	$213.85	11.371%	$238.1669	$238.17	$238.15	$238.20
Purchase #3	$88.78	13.104%	$100.4137	$100.41	$100.40	$100.40
Purchase #4	$64.80	11.366%	$72.1652	$72.17	$72.15	$72.20
Purchase #5	$55.30	12.843%	$62.4022	$62.40	$62.40	$62.40
Purchase #6	$122.30	5.729%	$129.3066	$129.31	$129.30	$129.30
Purchase #7	$219.49	11.213%	$244.1014	$244.10	$244.10	$244.10
7 purchase totals =	$995.29		$1,104.7092	$1,104.71	$1,104.65	$1,104.80