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	$156.50	9.727%	$171.7228	$171.72	$171.70	$171.70
Purchase #2	$237.75	10.458%	$262.6139	$262.61	$262.60	$262.60
Purchase #3	$26.92	7.752%	$29.0068	$29.01	$29.00	$29.00
Purchase #4	$184.43	6.393%	$196.2206	$196.22	$196.20	$196.20
Purchase #5	$96.28	9.523%	$105.4487	$105.45	$105.45	$105.40
Purchase #6	$241.97	6.656%	$258.0755	$258.08	$258.10	$258.10
Purchase #7	$92.67	4.120%	$96.488	$96.49	$96.50	$96.50
7 purchase totals =	$1,036.52		$1,119.5763	$1,119.58	$1,119.55	$1,119.50