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	$49.39	4.815%	$51.7681	$51.77	$51.75	$51.80
Purchase #2	$109.60	4.612%	$114.6548	$114.65	$114.65	$114.70
Purchase #3	$48.44	10.300%	$53.4293	$53.43	$53.45	$53.40
Purchase #4	$111.64	4.348%	$116.4941	$116.49	$116.50	$116.50
Purchase #5	$164.88	12.864%	$186.0902	$186.09	$186.10	$186.10
Purchase #6	$224.97	11.542%	$250.936	$250.94	$250.95	$250.90
Purchase #7	$73.90	11.804%	$82.6232	$82.62	$82.60	$82.60
7 purchase totals =	$782.82		$855.9957	$855.99	$856.00	$856.00