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	$153.29	7.509%	$164.8005	$164.80	$164.80	$164.80
Purchase #2	$240.72	10.192%	$265.2542	$265.25	$265.25	$265.30
Purchase #3	$33.39	8.487%	$36.2238	$36.22	$36.20	$36.20
Purchase #4	$139.34	8.580%	$151.2954	$151.30	$151.30	$151.30
Purchase #5	$19.69	4.218%	$20.5205	$20.52	$20.50	$20.50
Purchase #6	$127.96	4.557%	$133.7911	$133.79	$133.80	$133.80
Purchase #7	$208.54	5.733%	$220.4956	$220.50	$220.50	$220.50
7 purchase totals =	$922.93		$992.3811	$992.38	$992.35	$992.40