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	$138.25	4.503%	$144.4754	$144.48	$144.50	$144.50
Purchase #2	$13.28	3.105%	$13.6923	$13.69	$13.70	$13.70
Purchase #3	$38.52	12.581%	$43.3662	$43.37	$43.35	$43.40
Purchase #4	$179.53	8.393%	$194.598	$194.60	$194.60	$194.60
Purchase #5	$178.43	5.740%	$188.6719	$188.67	$188.65	$188.70
Purchase #6	$115.68	10.164%	$127.4377	$127.44	$127.45	$127.40
Purchase #7	$130.78	9.457%	$143.1479	$143.15	$143.15	$143.10
7 purchase totals =	$794.47		$855.3894	$855.40	$855.40	$855.40