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	$131.58	11.152%	$146.2538	$146.25	$146.25	$146.30
Purchase #2	$157.47	4.710%	$164.8868	$164.89	$164.90	$164.90
Purchase #3	$10.67	11.576%	$11.9052	$11.91	$11.90	$11.90
Purchase #4	$119.39	5.696%	$126.1905	$126.19	$126.20	$126.20
Purchase #5	$114.86	7.798%	$123.8168	$123.82	$123.80	$123.80
Purchase #6	$118.79	10.259%	$130.9767	$130.98	$131.00	$131.00
Purchase #7	$160.71	6.420%	$171.0276	$171.03	$171.05	$171.00
7 purchase totals =	$813.47		$875.0574	$875.07	$875.10	$875.10