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	$153.86	5.640%	$162.5377	$162.54	$162.55	$162.50
Purchase #2	$19.67	12.406%	$22.1103	$22.11	$22.10	$22.10
Purchase #3	$59.47	11.625%	$66.3834	$66.38	$66.40	$66.40
Purchase #4	$103.53	10.694%	$114.6015	$114.60	$114.60	$114.60
Purchase #5	$138.64	9.590%	$151.9356	$151.94	$151.95	$151.90
Purchase #6	$16.69	8.587%	$18.1232	$18.12	$18.10	$18.10
Purchase #7	$80.43	11.353%	$89.5612	$89.56	$89.55	$89.60
7 purchase totals =	$572.29		$625.2529	$625.25	$625.25	$625.20