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	$150.38	9.536%	$164.7202	$164.72	$164.70	$164.70
Purchase #2	$18.53	3.271%	$19.1361	$19.14	$19.15	$19.10
Purchase #3	$87.40	12.607%	$98.4185	$98.42	$98.40	$98.40
Purchase #4	$142.39	12.687%	$160.455	$160.46	$160.45	$160.50
Purchase #5	$161.89	10.198%	$178.3995	$178.40	$178.40	$178.40
Purchase #6	$176.86	7.517%	$190.1546	$190.15	$190.15	$190.20
Purchase #7	$159.66	4.773%	$167.2806	$167.28	$167.30	$167.30
7 purchase totals =	$897.11		$978.5645	$978.57	$978.55	$978.60