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	$35.77	13.493%	$40.5964	$40.60	$40.60	$40.60
Purchase #2	$132.32	9.775%	$145.2543	$145.25	$145.25	$145.30
Purchase #3	$223.51	12.497%	$251.442	$251.44	$251.45	$251.40
Purchase #4	$150.51	6.828%	$160.7868	$160.79	$160.80	$160.80
Purchase #5	$145.36	5.410%	$153.224	$153.22	$153.20	$153.20
Purchase #6	$138.95	7.176%	$148.9211	$148.92	$148.90	$148.90
Purchase #7	$110.64	5.262%	$116.4619	$116.46	$116.45	$116.50
7 purchase totals =	$937.06		$1,016.6865	$1,016.68	$1,016.65	$1,016.70