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	$91.98	7.196%	$98.5989	$98.60	$98.60	$98.60
Purchase #2	$13.48	11.724%	$15.0604	$15.06	$15.05	$15.10
Purchase #3	$167.46	10.393%	$184.8641	$184.86	$184.85	$184.90
Purchase #4	$234.55	11.839%	$262.3184	$262.32	$262.30	$262.30
Purchase #5	$134.60	13.116%	$152.2541	$152.25	$152.25	$152.30
Purchase #6	$192.65	12.365%	$216.4712	$216.47	$216.45	$216.50
Purchase #7	$12.36	4.598%	$12.9283	$12.93	$12.95	$12.90
7 purchase totals =	$847.08		$942.4954	$942.49	$942.45	$942.60