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	$85.67	6.564%	$91.2934	$91.29	$91.30	$91.30
Purchase #2	$10.95	6.464%	$11.6578	$11.66	$11.65	$11.70
Purchase #3	$192.96	4.151%	$200.9698	$200.97	$200.95	$201.00
Purchase #4	$163.77	5.815%	$173.2932	$173.29	$173.30	$173.30
Purchase #5	$134.59	5.276%	$141.691	$141.69	$141.70	$141.70
Purchase #6	$18.40	11.706%	$20.5539	$20.55	$20.55	$20.60
Purchase #7	$81.76	10.825%	$90.6105	$90.61	$90.60	$90.60
7 purchase totals =	$688.10		$730.0696	$730.06	$730.05	$730.20