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	$31.54	3.362%	$32.6004	$32.60	$32.60	$32.60
Purchase #2	$43.40	12.713%	$48.9174	$48.92	$48.90	$48.90
Purchase #3	$169.41	11.321%	$188.5889	$188.59	$188.60	$188.60
Purchase #4	$17.65	11.182%	$19.6236	$19.62	$19.60	$19.60
Purchase #5	$112.93	12.324%	$126.8475	$126.85	$126.85	$126.80
Purchase #6	$53.42	4.834%	$56.0023	$56.00	$56.00	$56.00
Purchase #7	$53.98	10.202%	$59.487	$59.49	$59.50	$59.50
7 purchase totals =	$482.33		$532.0671	$532.07	$532.05	$532.00