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	$162.85	10.154%	$179.3858	$179.39	$179.40	$179.40
Purchase #2	$208.75	11.821%	$233.4263	$233.43	$233.45	$233.40
Purchase #3	$226.65	6.409%	$241.176	$241.18	$241.20	$241.20
Purchase #4	$100.40	10.581%	$111.0233	$111.02	$111.00	$111.00
Purchase #5	$187.42	9.561%	$205.3392	$205.34	$205.35	$205.30
Purchase #6	$148.77	10.465%	$164.3388	$164.34	$164.35	$164.30
Purchase #7	$109.25	8.276%	$118.2915	$118.29	$118.30	$118.30
7 purchase totals =	$1,144.09		$1,252.9809	$1,252.99	$1,253.05	$1,252.90