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	$142.67	9.434%	$156.1295	$156.13	$156.15	$156.10
Purchase #2	$35.42	6.718%	$37.7995	$37.80	$37.80	$37.80
Purchase #3	$12.81	10.253%	$14.1234	$14.12	$14.10	$14.10
Purchase #4	$167.59	10.273%	$184.8065	$184.81	$184.80	$184.80
Purchase #5	$38.46	4.738%	$40.2822	$40.28	$40.30	$40.30
Purchase #6	$150.67	10.460%	$166.4301	$166.43	$166.45	$166.40
Purchase #7	$108.79	8.864%	$118.4331	$118.43	$118.45	$118.40
7 purchase totals =	$656.41		$718.0043	$718.00	$718.05	$717.90