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	$134.37	12.477%	$151.1353	$151.14	$151.15	$151.10
Purchase #2	$101.45	3.852%	$105.3579	$105.36	$105.35	$105.40
Purchase #3	$36.38	5.252%	$38.2907	$38.29	$38.30	$38.30
Purchase #4	$97.97	5.595%	$103.4514	$103.45	$103.45	$103.50
Purchase #5	$29.49	7.140%	$31.5956	$31.60	$31.60	$31.60
Purchase #6	$54.42	4.585%	$56.9152	$56.92	$56.90	$56.90
Purchase #7	$116.94	11.592%	$130.4957	$130.50	$130.50	$130.50
7 purchase totals =	$571.02		$617.2418	$617.26	$617.25	$617.30