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	$139.32	11.615%	$155.502	$155.50	$155.50	$155.50
Purchase #2	$78.87	13.167%	$89.2548	$89.25	$89.25	$89.30
Purchase #3	$164.70	3.167%	$169.916	$169.92	$169.90	$169.90
Purchase #4	$239.94	8.105%	$259.3871	$259.39	$259.40	$259.40
Purchase #5	$129.31	4.270%	$134.8315	$134.83	$134.85	$134.80
Purchase #6	$146.42	7.321%	$157.1394	$157.14	$157.15	$157.10
Purchase #7	$93.99	3.634%	$97.4056	$97.41	$97.40	$97.40
7 purchase totals =	$992.55		$1,063.4364	$1,063.44	$1,063.45	$1,063.40