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	$172.75	7.483%	$185.6769	$185.68	$185.70	$185.70
Purchase #2	$185.82	4.727%	$194.6037	$194.60	$194.60	$194.60
Purchase #3	$59.60	9.845%	$65.4676	$65.47	$65.45	$65.50
Purchase #4	$158.61	8.531%	$172.141	$172.14	$172.15	$172.10
Purchase #5	$12.97	10.360%	$14.3137	$14.31	$14.30	$14.30
Purchase #6	$196.49	11.815%	$219.7053	$219.71	$219.70	$219.70
Purchase #7	$23.64	4.549%	$24.7154	$24.72	$24.70	$24.70
7 purchase totals =	$809.88		$876.6236	$876.63	$876.60	$876.60