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	$146.88	9.208%	$160.4047	$160.40	$160.40	$160.40
Purchase #2	$153.71	12.457%	$172.8577	$172.86	$172.85	$172.90
Purchase #3	$146.26	12.663%	$164.7809	$164.78	$164.80	$164.80
Purchase #4	$61.54	4.625%	$64.3862	$64.39	$64.40	$64.40
Purchase #5	$244.42	10.491%	$270.0621	$270.06	$270.05	$270.10
Purchase #6	$125.44	4.307%	$130.8427	$130.84	$130.85	$130.80
Purchase #7	$108.68	13.461%	$123.3094	$123.31	$123.30	$123.30
7 purchase totals =	$986.93		$1,086.6437	$1,086.64	$1,086.65	$1,086.70