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	$43.33	11.695%	$48.3974	$48.40	$48.40	$48.40
Purchase #2	$203.80	6.779%	$217.6156	$217.62	$217.60	$217.60
Purchase #3	$38.88	11.271%	$43.2622	$43.26	$43.25	$43.30
Purchase #4	$147.97	3.286%	$152.8323	$152.83	$152.85	$152.80
Purchase #5	$128.39	4.760%	$134.5014	$134.50	$134.50	$134.50
Purchase #6	$246.55	5.376%	$259.8045	$259.80	$259.80	$259.80
Purchase #7	$96.49	3.674%	$100.035	$100.04	$100.05	$100.00
7 purchase totals =	$905.41		$956.4484	$956.45	$956.45	$956.40