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	$223.52	5.805%	$236.4953	$236.50	$236.50	$236.50
Purchase #2	$14.28	7.642%	$15.3713	$15.37	$15.35	$15.40
Purchase #3	$243.81	9.144%	$266.104	$266.10	$266.10	$266.10
Purchase #4	$19.32	12.838%	$21.8003	$21.80	$21.80	$21.80
Purchase #5	$131.89	4.604%	$137.9622	$137.96	$137.95	$138.00
Purchase #6	$168.45	13.332%	$190.9078	$190.91	$190.90	$190.90
Purchase #7	$182.31	9.332%	$199.3232	$199.32	$199.30	$199.30
7 purchase totals =	$983.58		$1,067.9641	$1,067.96	$1,067.90	$1,068.00