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	$46.34	3.308%	$47.8729	$47.87	$47.85	$47.90
Purchase #2	$141.78	13.358%	$160.719	$160.72	$160.70	$160.70
Purchase #3	$34.83	11.159%	$38.7167	$38.72	$38.70	$38.70
Purchase #4	$61.70	9.840%	$67.7713	$67.77	$67.75	$67.80
Purchase #5	$198.52	12.108%	$222.5568	$222.56	$222.55	$222.60
Purchase #6	$123.88	8.365%	$134.2426	$134.24	$134.25	$134.20
Purchase #7	$149.83	7.334%	$160.8185	$160.82	$160.80	$160.80
7 purchase totals =	$756.88		$832.6978	$832.70	$832.60	$832.70