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	$125.81	3.528%	$130.2486	$130.25	$130.25	$130.20
Purchase #2	$103.64	5.394%	$109.2303	$109.23	$109.25	$109.20
Purchase #3	$43.81	12.418%	$49.2503	$49.25	$49.25	$49.30
Purchase #4	$250.49	9.802%	$275.043	$275.04	$275.05	$275.00
Purchase #5	$91.96	11.316%	$102.3662	$102.37	$102.35	$102.40
Purchase #6	$149.52	12.268%	$167.8631	$167.86	$167.85	$167.90
Purchase #7	$66.67	7.373%	$71.5856	$71.59	$71.60	$71.60
7 purchase totals =	$831.90		$905.5871	$905.59	$905.60	$905.60