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	$111.25	6.453%	$118.429	$118.43	$118.45	$118.40
Purchase #2	$147.95	3.577%	$153.2422	$153.24	$153.25	$153.20
Purchase #3	$151.56	7.196%	$162.4663	$162.47	$162.45	$162.50
Purchase #4	$73.37	8.489%	$79.5984	$79.60	$79.60	$79.60
Purchase #5	$30.42	13.777%	$34.611	$34.61	$34.60	$34.60
Purchase #6	$145.90	7.191%	$156.3917	$156.39	$156.40	$156.40
Purchase #7	$82.80	13.620%	$94.0774	$94.08	$94.10	$94.10
7 purchase totals =	$743.25		$798.8160	$798.82	$798.85	$798.80