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	$88.66	11.378%	$98.7477	$98.75	$98.75	$98.70
Purchase #2	$102.75	8.860%	$111.8537	$111.85	$111.85	$111.90
Purchase #3	$165.76	7.635%	$178.4158	$178.42	$178.40	$178.40
Purchase #4	$144.75	7.744%	$155.9594	$155.96	$155.95	$156.00
Purchase #5	$77.26	10.280%	$85.2023	$85.20	$85.20	$85.20
Purchase #6	$122.42	13.649%	$139.1291	$139.13	$139.15	$139.10
Purchase #7	$49.96	7.265%	$53.5896	$53.59	$53.60	$53.60
7 purchase totals =	$751.56		$822.8976	$822.90	$822.90	$822.90