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	$217.54	11.192%	$241.8871	$241.89	$241.90	$241.90
Purchase #2	$228.94	5.460%	$241.4401	$241.44	$241.45	$241.40
Purchase #3	$204.59	13.414%	$232.0337	$232.03	$232.05	$232.00
Purchase #4	$159.71	13.562%	$181.3699	$181.37	$181.35	$181.40
Purchase #5	$246.78	10.733%	$273.2669	$273.27	$273.25	$273.30
Purchase #6	$137.64	10.144%	$151.6022	$151.60	$151.60	$151.60
Purchase #7	$92.69	11.470%	$103.3215	$103.32	$103.30	$103.30
7 purchase totals =	$1,287.89		$1,424.9214	$1,424.92	$1,424.90	$1,424.90