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	$137.39	4.813%	$144.0026	$144.00	$144.00	$144.00
Purchase #2	$87.33	5.151%	$91.8284	$91.83	$91.85	$91.80
Purchase #3	$54.30	5.144%	$57.0932	$57.09	$57.10	$57.10
Purchase #4	$54.50	3.432%	$56.3704	$56.37	$56.35	$56.40
Purchase #5	$27.53	10.854%	$30.5181	$30.52	$30.50	$30.50
Purchase #6	$54.45	4.430%	$56.8621	$56.86	$56.85	$56.90
Purchase #7	$173.70	9.804%	$190.7295	$190.73	$190.75	$190.70
7 purchase totals =	$589.20		$627.4043	$627.40	$627.40	$627.40