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	$55.45	13.526%	$62.9502	$62.95	$62.95	$63.00
Purchase #2	$131.81	6.852%	$140.8416	$140.84	$140.85	$140.80
Purchase #3	$24.40	13.160%	$27.611	$27.61	$27.60	$27.60
Purchase #4	$105.76	3.864%	$109.8466	$109.85	$109.85	$109.80
Purchase #5	$11.39	6.719%	$12.1553	$12.16	$12.15	$12.20
Purchase #6	$40.38	6.666%	$43.0717	$43.07	$43.05	$43.10
Purchase #7	$244.34	4.845%	$256.1783	$256.18	$256.20	$256.20
7 purchase totals =	$613.53		$652.6547	$652.66	$652.65	$652.70