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	$133.25	13.423%	$151.1361	$151.14	$151.15	$151.10
Purchase #2	$198.57	6.559%	$211.5942	$211.59	$211.60	$211.60
Purchase #3	$75.80	10.212%	$83.5407	$83.54	$83.55	$83.50
Purchase #4	$153.71	6.840%	$164.2238	$164.22	$164.20	$164.20
Purchase #5	$41.29	10.430%	$45.5965	$45.60	$45.60	$45.60
Purchase #6	$214.79	13.828%	$244.4912	$244.49	$244.50	$244.50
Purchase #7	$29.63	11.637%	$33.078	$33.08	$33.10	$33.10
7 purchase totals =	$847.04		$933.6605	$933.66	$933.70	$933.60