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	$59.57	9.588%	$65.2816	$65.28	$65.30	$65.30
Purchase #2	$145.35	4.149%	$151.3806	$151.38	$151.40	$151.40
Purchase #3	$53.71	10.279%	$59.2309	$59.23	$59.25	$59.20
Purchase #4	$83.26	13.863%	$94.8023	$94.80	$94.80	$94.80
Purchase #5	$9.90	3.235%	$10.2203	$10.22	$10.20	$10.20
Purchase #6	$101.42	4.453%	$105.9362	$105.94	$105.95	$105.90
Purchase #7	$226.62	12.827%	$255.6885	$255.69	$255.70	$255.70
7 purchase totals =	$679.83		$742.5404	$742.54	$742.60	$742.50