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	$158.83	9.452%	$173.8426	$173.84	$173.85	$173.80
Purchase #2	$155.90	3.168%	$160.8389	$160.84	$160.85	$160.80
Purchase #3	$56.88	13.679%	$64.6606	$64.66	$64.65	$64.70
Purchase #4	$192.82	6.666%	$205.6734	$205.67	$205.65	$205.70
Purchase #5	$217.32	9.687%	$238.3718	$238.37	$238.35	$238.40
Purchase #6	$127.77	10.224%	$140.8332	$140.83	$140.85	$140.80
Purchase #7	$160.25	11.315%	$178.3823	$178.38	$178.40	$178.40
7 purchase totals =	$1,069.77		$1,162.6028	$1,162.59	$1,162.60	$1,162.60