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	$146.29	5.220%	$153.9263	$153.93	$153.95	$153.90
Purchase #2	$96.91	3.789%	$100.5819	$100.58	$100.60	$100.60
Purchase #3	$138.82	3.149%	$143.1914	$143.19	$143.20	$143.20
Purchase #4	$19.87	3.580%	$20.5813	$20.58	$20.60	$20.60
Purchase #5	$93.41	8.673%	$101.5114	$101.51	$101.50	$101.50
Purchase #6	$137.93	13.687%	$156.8085	$156.81	$156.80	$156.80
Purchase #7	$144.31	10.189%	$159.0137	$159.01	$159.00	$159.00
7 purchase totals =	$777.54		$835.6145	$835.61	$835.65	$835.60