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	$13.55	6.196%	$14.3896	$14.39	$14.40	$14.40
Purchase #2	$83.55	7.481%	$89.8004	$89.80	$89.80	$89.80
Purchase #3	$29.28	7.236%	$31.3987	$31.40	$31.40	$31.40
Purchase #4	$235.45	3.857%	$244.5313	$244.53	$244.55	$244.50
Purchase #5	$128.28	11.389%	$142.8898	$142.89	$142.90	$142.90
Purchase #6	$199.67	7.370%	$214.3857	$214.39	$214.40	$214.40
Purchase #7	$98.79	6.786%	$105.4939	$105.49	$105.50	$105.50
7 purchase totals =	$788.57		$842.8894	$842.89	$842.95	$842.90