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	$187.35	7.508%	$201.4162	$201.42	$201.40	$201.40
Purchase #2	$182.43	3.366%	$188.5706	$188.57	$188.55	$188.60
Purchase #3	$176.82	7.205%	$189.5599	$189.56	$189.55	$189.60
Purchase #4	$148.40	4.851%	$155.5989	$155.60	$155.60	$155.60
Purchase #5	$141.79	9.509%	$155.2728	$155.27	$155.25	$155.30
Purchase #6	$37.78	11.321%	$42.0571	$42.06	$42.05	$42.10
Purchase #7	$145.84	12.749%	$164.4331	$164.43	$164.45	$164.40
7 purchase totals =	$1,020.41		$1,096.9086	$1,096.91	$1,096.85	$1,097.00