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	$102.91	8.480%	$111.6368	$111.64	$111.65	$111.60
Purchase #2	$158.66	9.521%	$173.766	$173.77	$173.75	$173.80
Purchase #3	$164.68	8.416%	$178.5395	$178.54	$178.55	$178.50
Purchase #4	$167.64	12.379%	$188.3922	$188.39	$188.40	$188.40
Purchase #5	$42.50	3.118%	$43.8252	$43.83	$43.85	$43.80
Purchase #6	$182.78	9.238%	$199.6652	$199.67	$199.65	$199.70
Purchase #7	$169.50	12.118%	$190.04	$190.04	$190.05	$190.00
7 purchase totals =	$988.67		$1,085.8649	$1,085.88	$1,085.90	$1,085.80