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	$205.42	9.134%	$224.1831	$224.18	$224.20	$224.20
Purchase #2	$126.95	13.499%	$144.087	$144.09	$144.10	$144.10
Purchase #3	$145.92	8.859%	$158.8471	$158.85	$158.85	$158.80
Purchase #4	$150.48	9.273%	$164.434	$164.43	$164.45	$164.40
Purchase #5	$78.84	9.141%	$86.0468	$86.05	$86.05	$86.00
Purchase #6	$116.27	9.461%	$127.2703	$127.27	$127.25	$127.30
Purchase #7	$60.45	3.145%	$62.3512	$62.35	$62.35	$62.40
7 purchase totals =	$884.33		$967.2195	$967.22	$967.25	$967.20