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	$36.51	5.536%	$38.5312	$38.53	$38.55	$38.50
Purchase #2	$148.35	11.500%	$165.4103	$165.41	$165.40	$165.40
Purchase #3	$49.97	4.595%	$52.2661	$52.27	$52.25	$52.30
Purchase #4	$14.39	13.165%	$16.2844	$16.28	$16.30	$16.30
Purchase #5	$89.93	6.846%	$96.0866	$96.09	$96.10	$96.10
Purchase #6	$13.62	13.698%	$15.4857	$15.49	$15.50	$15.50
Purchase #7	$87.72	13.452%	$99.5201	$99.52	$99.50	$99.50
7 purchase totals =	$440.49		$483.5844	$483.59	$483.60	$483.60