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	$232.83	9.235%	$254.3319	$254.33	$254.35	$254.30
Purchase #2	$47.99	11.641%	$53.5765	$53.58	$53.60	$53.60
Purchase #3	$146.62	6.691%	$156.4303	$156.43	$156.45	$156.40
Purchase #4	$73.72	10.556%	$81.5019	$81.50	$81.50	$81.50
Purchase #5	$62.87	6.213%	$66.7761	$66.78	$66.80	$66.80
Purchase #6	$100.95	13.371%	$114.448	$114.45	$114.45	$114.40
Purchase #7	$244.52	13.219%	$276.8431	$276.84	$276.85	$276.80
7 purchase totals =	$909.50		$1,003.9078	$1,003.91	$1,004.00	$1,003.80