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	$24.86	6.376%	$26.4451	$26.45	$26.45	$26.40
Purchase #2	$143.83	13.237%	$162.8688	$162.87	$162.85	$162.90
Purchase #3	$29.56	9.530%	$32.3771	$32.38	$32.40	$32.40
Purchase #4	$135.76	10.874%	$150.5225	$150.52	$150.50	$150.50
Purchase #5	$193.50	3.833%	$200.9169	$200.92	$200.90	$200.90
Purchase #6	$234.68	13.601%	$266.5988	$266.60	$266.60	$266.60
Purchase #7	$49.85	10.393%	$55.0309	$55.03	$55.05	$55.00
7 purchase totals =	$812.04		$894.7601	$894.77	$894.75	$894.70