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	$108.43	9.227%	$118.4348	$118.43	$118.45	$118.40
Purchase #2	$225.90	5.107%	$237.4367	$237.44	$237.45	$237.40
Purchase #3	$96.46	12.758%	$108.7664	$108.77	$108.75	$108.80
Purchase #4	$37.67	11.548%	$42.0201	$42.02	$42.00	$42.00
Purchase #5	$28.78	13.242%	$32.591	$32.59	$32.60	$32.60
Purchase #6	$145.74	8.283%	$157.8116	$157.81	$157.80	$157.80
Purchase #7	$84.39	7.584%	$90.7901	$90.79	$90.80	$90.80
7 purchase totals =	$727.37		$787.8507	$787.85	$787.85	$787.80