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	$153.38	5.607%	$161.98	$161.98	$162.00	$162.00
Purchase #2	$36.62	10.851%	$40.5936	$40.59	$40.60	$40.60
Purchase #3	$156.71	10.424%	$173.0455	$173.05	$173.05	$173.00
Purchase #4	$139.83	8.647%	$151.9211	$151.92	$151.90	$151.90
Purchase #5	$10.83	11.642%	$12.0908	$12.09	$12.10	$12.10
Purchase #6	$38.73	12.141%	$43.4322	$43.43	$43.45	$43.40
Purchase #7	$19.80	7.291%	$21.2436	$21.24	$21.25	$21.20
7 purchase totals =	$555.90		$604.3068	$604.30	$604.35	$604.20