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	$237.58	10.627%	$262.8276	$262.83	$262.85	$262.80
Purchase #2	$140.67	11.326%	$156.6023	$156.60	$156.60	$156.60
Purchase #3	$101.31	4.510%	$105.8791	$105.88	$105.90	$105.90
Purchase #4	$95.54	5.462%	$100.7584	$100.76	$100.75	$100.80
Purchase #5	$89.40	10.452%	$98.7441	$98.74	$98.75	$98.70
Purchase #6	$89.30	13.245%	$101.1278	$101.13	$101.15	$101.10
Purchase #7	$130.33	7.291%	$139.8324	$139.83	$139.85	$139.80
7 purchase totals =	$884.13		$965.7717	$965.77	$965.85	$965.70