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	$222.94	9.660%	$244.476	$244.48	$244.50	$244.50
Purchase #2	$223.53	13.321%	$253.3064	$253.31	$253.30	$253.30
Purchase #3	$250.86	11.855%	$280.5995	$280.60	$280.60	$280.60
Purchase #4	$149.47	12.251%	$167.7816	$167.78	$167.80	$167.80
Purchase #5	$35.91	6.191%	$38.1332	$38.13	$38.15	$38.10
Purchase #6	$125.84	13.219%	$142.4748	$142.47	$142.45	$142.50
Purchase #7	$100.87	12.534%	$113.513	$113.51	$113.50	$113.50
7 purchase totals =	$1,109.42		$1,240.2845	$1,240.28	$1,240.30	$1,240.30