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	$155.92	4.491%	$162.9224	$162.92	$162.90	$162.90
Purchase #2	$104.69	13.208%	$118.5175	$118.52	$118.50	$118.50
Purchase #3	$97.85	13.561%	$111.1194	$111.12	$111.10	$111.10
Purchase #4	$84.67	4.119%	$88.1576	$88.16	$88.15	$88.20
Purchase #5	$163.66	12.371%	$183.9064	$183.91	$183.90	$183.90
Purchase #6	$157.64	5.308%	$166.0075	$166.01	$166.00	$166.00
Purchase #7	$19.82	8.208%	$21.4468	$21.45	$21.45	$21.40
7 purchase totals =	$784.25		$852.0776	$852.09	$852.00	$852.00