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	$92.54	10.338%	$102.1068	$102.11	$102.10	$102.10
Purchase #2	$101.54	4.321%	$105.9275	$105.93	$105.95	$105.90
Purchase #3	$93.60	10.524%	$103.4505	$103.45	$103.45	$103.50
Purchase #4	$114.46	3.491%	$118.4558	$118.46	$118.45	$118.50
Purchase #5	$43.92	10.687%	$48.6137	$48.61	$48.60	$48.60
Purchase #6	$11.86	8.648%	$12.8857	$12.89	$12.90	$12.90
Purchase #7	$49.29	8.481%	$53.4703	$53.47	$53.45	$53.50
7 purchase totals =	$507.21		$544.9103	$544.92	$544.90	$545.00