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	$142.96	11.134%	$158.8772	$158.88	$158.90	$158.90
Purchase #2	$183.35	13.828%	$208.7036	$208.70	$208.70	$208.70
Purchase #3	$80.48	11.613%	$89.8261	$89.83	$89.85	$89.80
Purchase #4	$53.79	11.704%	$60.0856	$60.09	$60.10	$60.10
Purchase #5	$151.55	13.482%	$171.982	$171.98	$172.00	$172.00
Purchase #6	$220.76	4.271%	$230.1887	$230.19	$230.20	$230.20
Purchase #7	$80.51	12.691%	$90.7275	$90.73	$90.75	$90.70
7 purchase totals =	$913.40		$1,010.3907	$1,010.40	$1,010.50	$1,010.40