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	$42.29	13.649%	$48.0622	$48.06	$48.05	$48.10
Purchase #2	$194.52	5.430%	$205.0824	$205.08	$205.10	$205.10
Purchase #3	$150.78	5.800%	$159.5252	$159.53	$159.55	$159.50
Purchase #4	$194.39	13.119%	$219.892	$219.89	$219.90	$219.90
Purchase #5	$42.56	13.676%	$48.3805	$48.38	$48.40	$48.40
Purchase #6	$103.58	3.446%	$107.1494	$107.15	$107.15	$107.10
Purchase #7	$133.93	5.504%	$141.3015	$141.30	$141.30	$141.30
7 purchase totals =	$862.05		$929.3932	$929.39	$929.45	$929.40