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	$121.98	7.838%	$131.5408	$131.54	$131.55	$131.50
Purchase #2	$94.57	6.637%	$100.8466	$100.85	$100.85	$100.80
Purchase #3	$222.32	8.708%	$241.6796	$241.68	$241.70	$241.70
Purchase #4	$98.27	6.265%	$104.4266	$104.43	$104.45	$104.40
Purchase #5	$47.75	8.314%	$51.7199	$51.72	$51.70	$51.70
Purchase #6	$244.96	10.694%	$271.156	$271.16	$271.15	$271.20
Purchase #7	$134.55	12.664%	$151.5894	$151.59	$151.60	$151.60
7 purchase totals =	$964.40		$1,052.9589	$1,052.97	$1,053.00	$1,052.90