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	$148.43	5.621%	$156.7733	$156.77	$156.75	$156.80
Purchase #2	$13.87	5.151%	$14.5844	$14.58	$14.60	$14.60
Purchase #3	$69.38	3.804%	$72.0192	$72.02	$72.00	$72.00
Purchase #4	$96.42	12.839%	$108.7994	$108.80	$108.80	$108.80
Purchase #5	$111.90	10.460%	$123.6047	$123.60	$123.60	$123.60
Purchase #6	$9.35	8.111%	$10.1084	$10.11	$10.10	$10.10
Purchase #7	$42.77	6.863%	$45.7053	$45.71	$45.70	$45.70
7 purchase totals =	$492.12		$531.5947	$531.59	$531.55	$531.60