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	$155.84	11.229%	$173.3393	$173.34	$173.35	$173.30
Purchase #2	$103.29	13.189%	$116.9129	$116.91	$116.90	$116.90
Purchase #3	$249.85	10.867%	$277.0012	$277.00	$277.00	$277.00
Purchase #4	$219.85	12.671%	$247.7072	$247.71	$247.70	$247.70
Purchase #5	$122.43	8.320%	$132.6162	$132.62	$132.60	$132.60
Purchase #6	$69.89	3.198%	$72.1251	$72.13	$72.15	$72.10
Purchase #7	$73.63	6.356%	$78.3099	$78.31	$78.30	$78.30
7 purchase totals =	$994.78		$1,098.0118	$1,098.02	$1,098.00	$1,097.90