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	$67.75	4.382%	$70.7188	$70.72	$70.70	$70.70
Purchase #2	$192.84	12.849%	$217.618	$217.62	$217.60	$217.60
Purchase #3	$152.51	13.669%	$173.3566	$173.36	$173.35	$173.40
Purchase #4	$202.61	4.453%	$211.6322	$211.63	$211.65	$211.60
Purchase #5	$113.73	12.617%	$128.0793	$128.08	$128.10	$128.10
Purchase #6	$126.53	10.501%	$139.8169	$139.82	$139.80	$139.80
Purchase #7	$95.91	10.172%	$105.666	$105.67	$105.65	$105.70
7 purchase totals =	$951.88		$1,046.8878	$1,046.90	$1,046.85	$1,046.90