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	$112.42	13.572%	$127.6776	$127.68	$127.70	$127.70
Purchase #2	$183.82	12.210%	$206.2644	$206.26	$206.25	$206.30
Purchase #3	$88.94	13.856%	$101.2635	$101.26	$101.25	$101.30
Purchase #4	$194.89	6.749%	$208.0431	$208.04	$208.05	$208.00
Purchase #5	$135.59	4.677%	$141.9315	$141.93	$141.95	$141.90
Purchase #6	$31.55	4.162%	$32.8631	$32.86	$32.85	$32.90
Purchase #7	$107.31	7.738%	$115.6136	$115.61	$115.60	$115.60
7 purchase totals =	$854.52		$933.6568	$933.64	$933.65	$933.70