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	$34.54	11.273%	$38.4337	$38.43	$38.45	$38.40
Purchase #2	$20.63	4.594%	$21.5777	$21.58	$21.60	$21.60
Purchase #3	$145.78	3.390%	$150.7219	$150.72	$150.70	$150.70
Purchase #4	$158.59	5.800%	$167.7882	$167.79	$167.80	$167.80
Purchase #5	$228.62	10.412%	$252.4239	$252.42	$252.40	$252.40
Purchase #6	$14.60	6.155%	$15.4986	$15.50	$15.50	$15.50
Purchase #7	$6.89	13.717%	$7.8351	$7.84	$7.85	$7.80
7 purchase totals =	$609.65		$654.2791	$654.28	$654.30	$654.20