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	$105.39	6.128%	$111.8483	$111.85	$111.85	$111.80
Purchase #2	$18.87	3.805%	$19.588	$19.59	$19.60	$19.60
Purchase #3	$170.43	12.649%	$191.9877	$191.99	$192.00	$192.00
Purchase #4	$112.27	12.609%	$126.4261	$126.43	$126.45	$126.40
Purchase #5	$112.60	13.164%	$127.4227	$127.42	$127.40	$127.40
Purchase #6	$40.44	11.581%	$45.1234	$45.12	$45.10	$45.10
Purchase #7	$230.61	11.211%	$256.4637	$256.46	$256.45	$256.50
7 purchase totals =	$790.61		$878.8599	$878.86	$878.85	$878.80