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	$145.52	10.202%	$160.366	$160.37	$160.35	$160.40
Purchase #2	$71.68	12.849%	$80.8902	$80.89	$80.90	$80.90
Purchase #3	$39.64	8.443%	$42.9868	$42.99	$43.00	$43.00
Purchase #4	$50.54	6.713%	$53.9328	$53.93	$53.95	$53.90
Purchase #5	$112.47	13.141%	$127.2497	$127.25	$127.25	$127.20
Purchase #6	$60.98	5.509%	$64.3394	$64.34	$64.35	$64.30
Purchase #7	$139.37	4.849%	$146.1281	$146.13	$146.15	$146.10
7 purchase totals =	$620.20		$675.8930	$675.90	$675.95	$675.80