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	$218.30	8.371%	$236.5739	$236.57	$236.55	$236.60
Purchase #2	$202.83	13.294%	$229.7942	$229.79	$229.80	$229.80
Purchase #3	$234.46	10.716%	$259.5847	$259.58	$259.60	$259.60
Purchase #4	$10.68	7.321%	$11.4619	$11.46	$11.45	$11.50
Purchase #5	$184.38	4.591%	$192.8449	$192.84	$192.85	$192.80
Purchase #6	$130.38	13.838%	$148.422	$148.42	$148.40	$148.40
Purchase #7	$50.92	4.542%	$53.2328	$53.23	$53.25	$53.20
7 purchase totals =	$1,031.95		$1,131.9144	$1,131.89	$1,131.90	$1,131.90