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	$211.63	4.540%	$221.238	$221.24	$221.25	$221.20
Purchase #2	$104.47	7.762%	$112.579	$112.58	$112.60	$112.60
Purchase #3	$163.32	11.714%	$182.4513	$182.45	$182.45	$182.50
Purchase #4	$155.78	7.579%	$167.5866	$167.59	$167.60	$167.60
Purchase #5	$95.87	10.424%	$105.8635	$105.86	$105.85	$105.90
Purchase #6	$35.51	10.187%	$39.1274	$39.13	$39.15	$39.10
Purchase #7	$35.88	9.329%	$39.2272	$39.23	$39.25	$39.20
7 purchase totals =	$802.46		$868.0730	$868.08	$868.15	$868.10