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	$49.60	10.502%	$54.809	$54.81	$54.80	$54.80
Purchase #2	$99.63	9.462%	$109.057	$109.06	$109.05	$109.10
Purchase #3	$146.67	11.593%	$163.6735	$163.67	$163.65	$163.70
Purchase #4	$100.90	10.284%	$111.2766	$111.28	$111.30	$111.30
Purchase #5	$112.97	3.175%	$116.5568	$116.56	$116.55	$116.60
Purchase #6	$175.93	12.714%	$198.2977	$198.30	$198.30	$198.30
Purchase #7	$225.96	3.216%	$233.2269	$233.23	$233.25	$233.20
7 purchase totals =	$911.66		$986.8975	$986.91	$986.90	$987.00