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	$72.86	6.447%	$77.5573	$77.56	$77.55	$77.60
Purchase #2	$248.51	4.869%	$260.61	$260.61	$260.60	$260.60
Purchase #3	$158.52	10.823%	$175.6766	$175.68	$175.70	$175.70
Purchase #4	$213.78	6.401%	$227.4641	$227.46	$227.45	$227.50
Purchase #5	$245.73	11.720%	$274.5296	$274.53	$274.55	$274.50
Purchase #6	$48.83	12.403%	$54.8864	$54.89	$54.90	$54.90
Purchase #7	$56.68	10.368%	$62.5566	$62.56	$62.55	$62.60
7 purchase totals =	$1,044.91		$1,133.2806	$1,133.29	$1,133.30	$1,133.40