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	$178.85	6.568%	$190.5969	$190.60	$190.60	$190.60
Purchase #2	$60.76	9.391%	$66.466	$66.47	$66.45	$66.50
Purchase #3	$225.49	6.242%	$239.5651	$239.57	$239.55	$239.60
Purchase #4	$151.94	4.535%	$158.8305	$158.83	$158.85	$158.80
Purchase #5	$40.32	4.649%	$42.1945	$42.19	$42.20	$42.20
Purchase #6	$168.50	13.324%	$190.9509	$190.95	$190.95	$191.00
Purchase #7	$244.72	6.275%	$260.0762	$260.08	$260.10	$260.10
7 purchase totals =	$1,070.58		$1,148.6801	$1,148.69	$1,148.70	$1,148.80