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	$213.81	4.649%	$223.75	$223.75	$223.75	$223.80
Purchase #2	$41.76	3.823%	$43.3565	$43.36	$43.35	$43.40
Purchase #3	$63.80	13.429%	$72.3677	$72.37	$72.35	$72.40
Purchase #4	$130.70	10.481%	$144.3987	$144.40	$144.40	$144.40
Purchase #5	$245.78	8.685%	$267.126	$267.13	$267.15	$267.10
Purchase #6	$181.36	5.235%	$190.8542	$190.85	$190.85	$190.90
Purchase #7	$33.68	13.557%	$38.246	$38.25	$38.25	$38.20
7 purchase totals =	$910.89		$980.0991	$980.11	$980.10	$980.20