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	$205.72	5.705%	$217.4563	$217.46	$217.45	$217.50
Purchase #2	$47.89	3.812%	$49.7156	$49.72	$49.70	$49.70
Purchase #3	$78.49	5.603%	$82.8878	$82.89	$82.90	$82.90
Purchase #4	$47.49	13.696%	$53.9942	$53.99	$54.00	$54.00
Purchase #5	$105.55	3.772%	$109.5313	$109.53	$109.55	$109.50
Purchase #6	$64.87	11.311%	$72.2074	$72.21	$72.20	$72.20
Purchase #7	$119.71	3.423%	$123.8077	$123.81	$123.80	$123.80
7 purchase totals =	$669.72		$709.6003	$709.61	$709.60	$709.60