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	$241.27	5.114%	$253.6085	$253.61	$253.60	$253.60
Purchase #2	$111.51	10.774%	$123.5241	$123.52	$123.50	$123.50
Purchase #3	$190.69	9.609%	$209.0134	$209.01	$209.00	$209.00
Purchase #4	$86.73	5.865%	$91.8167	$91.82	$91.80	$91.80
Purchase #5	$62.48	5.723%	$66.0557	$66.06	$66.05	$66.10
Purchase #6	$176.88	9.698%	$194.0338	$194.03	$194.05	$194.00
Purchase #7	$205.92	4.359%	$214.8961	$214.90	$214.90	$214.90
7 purchase totals =	$1,075.48		$1,152.9483	$1,152.95	$1,152.90	$1,152.90