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	$87.60	5.749%	$92.6361	$92.64	$92.65	$92.60
Purchase #2	$22.69	12.525%	$25.5319	$25.53	$25.55	$25.50
Purchase #3	$109.77	6.463%	$116.8644	$116.86	$116.85	$116.90
Purchase #4	$127.35	11.840%	$142.4282	$142.43	$142.45	$142.40
Purchase #5	$36.99	11.848%	$41.3726	$41.37	$41.35	$41.40
Purchase #6	$6.57	3.178%	$6.7788	$6.78	$6.80	$6.80
Purchase #7	$102.84	3.478%	$106.4168	$106.42	$106.40	$106.40
7 purchase totals =	$493.81		$532.0288	$532.03	$532.05	$532.00