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	$164.38	13.514%	$186.5943	$186.59	$186.60	$186.60
Purchase #2	$215.37	5.864%	$227.9993	$228.00	$228.00	$228.00
Purchase #3	$70.47	10.704%	$78.0131	$78.01	$78.00	$78.00
Purchase #4	$228.40	5.627%	$241.2521	$241.25	$241.25	$241.30
Purchase #5	$210.99	5.845%	$223.3224	$223.32	$223.30	$223.30
Purchase #6	$12.83	3.325%	$13.2566	$13.26	$13.25	$13.30
Purchase #7	$100.78	10.570%	$111.4324	$111.43	$111.45	$111.40
7 purchase totals =	$1,003.22		$1,081.8702	$1,081.86	$1,081.85	$1,081.90