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	$81.43	4.858%	$85.3859	$85.39	$85.40	$85.40
Purchase #2	$83.72	8.218%	$90.6001	$90.60	$90.60	$90.60
Purchase #3	$152.76	6.389%	$162.5198	$162.52	$162.50	$162.50
Purchase #4	$8.67	10.574%	$9.5868	$9.59	$9.60	$9.60
Purchase #5	$155.56	11.326%	$173.1787	$173.18	$173.20	$173.20
Purchase #6	$151.64	7.476%	$162.9766	$162.98	$163.00	$163.00
Purchase #7	$145.25	12.614%	$163.5718	$163.57	$163.55	$163.60
7 purchase totals =	$779.03		$847.8197	$847.83	$847.85	$847.90