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	$142.52	5.508%	$150.37	$150.37	$150.35	$150.40
Purchase #2	$138.46	4.447%	$144.6173	$144.62	$144.60	$144.60
Purchase #3	$217.53	9.376%	$237.9256	$237.93	$237.95	$237.90
Purchase #4	$101.67	10.869%	$112.7205	$112.72	$112.70	$112.70
Purchase #5	$55.61	12.852%	$62.757	$62.76	$62.75	$62.80
Purchase #6	$153.69	13.508%	$174.4504	$174.45	$174.45	$174.50
Purchase #7	$47.80	12.328%	$53.6928	$53.69	$53.70	$53.70
7 purchase totals =	$857.28		$936.5336	$936.54	$936.50	$936.60