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	$74.95	11.566%	$83.6187	$83.62	$83.60	$83.60
Purchase #2	$29.64	7.156%	$31.761	$31.76	$31.75	$31.80
Purchase #3	$134.41	3.849%	$139.5834	$139.58	$139.60	$139.60
Purchase #4	$31.49	10.583%	$34.8226	$34.82	$34.80	$34.80
Purchase #5	$167.70	11.847%	$187.5674	$187.57	$187.55	$187.60
Purchase #6	$96.61	4.124%	$100.5942	$100.59	$100.60	$100.60
Purchase #7	$148.41	12.167%	$166.467	$166.47	$166.45	$166.50
7 purchase totals =	$683.21		$744.4143	$744.41	$744.35	$744.50