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	$241.46	10.521%	$266.864	$266.86	$266.85	$266.90
Purchase #2	$81.63	7.685%	$87.9033	$87.90	$87.90	$87.90
Purchase #3	$82.56	3.368%	$85.3406	$85.34	$85.35	$85.30
Purchase #4	$43.92	3.163%	$45.3092	$45.31	$45.30	$45.30
Purchase #5	$237.90	3.850%	$247.0592	$247.06	$247.05	$247.10
Purchase #6	$139.89	9.832%	$153.644	$153.64	$153.65	$153.60
Purchase #7	$142.58	11.221%	$158.5789	$158.58	$158.60	$158.60
7 purchase totals =	$969.94		$1,044.6992	$1,044.69	$1,044.70	$1,044.70