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	$244.51	5.802%	$258.6965	$258.70	$258.70	$258.70
Purchase #2	$223.86	13.607%	$254.3206	$254.32	$254.30	$254.30
Purchase #3	$145.58	5.476%	$153.552	$153.55	$153.55	$153.60
Purchase #4	$134.33	11.269%	$149.4676	$149.47	$149.45	$149.50
Purchase #5	$70.80	10.267%	$78.069	$78.07	$78.05	$78.10
Purchase #6	$250.54	8.326%	$271.4	$271.40	$271.40	$271.40
Purchase #7	$186.40	5.469%	$196.5942	$196.59	$196.60	$196.60
7 purchase totals =	$1,256.02		$1,362.0999	$1,362.10	$1,362.05	$1,362.20