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	$134.91	11.240%	$150.0739	$150.07	$150.05	$150.10
Purchase #2	$177.85	7.181%	$190.6214	$190.62	$190.60	$190.60
Purchase #3	$179.98	5.695%	$190.2299	$190.23	$190.25	$190.20
Purchase #4	$150.40	5.275%	$158.3336	$158.33	$158.35	$158.30
Purchase #5	$15.35	4.134%	$15.9846	$15.98	$16.00	$16.00
Purchase #6	$189.65	8.318%	$205.4251	$205.43	$205.45	$205.40
Purchase #7	$27.77	13.231%	$31.4442	$31.44	$31.45	$31.40
7 purchase totals =	$875.91		$942.1127	$942.10	$942.15	$942.00