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	$107.35	7.678%	$115.5923	$115.59	$115.60	$115.60
Purchase #2	$5.74	11.536%	$6.4022	$6.40	$6.40	$6.40
Purchase #3	$171.74	10.742%	$190.1883	$190.19	$190.20	$190.20
Purchase #4	$234.48	13.637%	$266.456	$266.46	$266.45	$266.50
Purchase #5	$190.28	3.204%	$196.3766	$196.38	$196.40	$196.40
Purchase #6	$175.94	13.697%	$200.0385	$200.04	$200.05	$200.00
Purchase #7	$54.91	3.374%	$56.7627	$56.76	$56.75	$56.80
7 purchase totals =	$940.44		$1,031.8166	$1,031.82	$1,031.85	$1,031.90