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	$167.67	13.525%	$190.3474	$190.35	$190.35	$190.30
Purchase #2	$205.33	6.146%	$217.9496	$217.95	$217.95	$217.90
Purchase #3	$67.68	4.641%	$70.821	$70.82	$70.80	$70.80
Purchase #4	$19.32	4.664%	$20.2211	$20.22	$20.20	$20.20
Purchase #5	$156.58	7.798%	$168.7901	$168.79	$168.80	$168.80
Purchase #6	$236.32	8.118%	$255.5045	$255.50	$255.50	$255.50
Purchase #7	$48.69	5.702%	$51.4663	$51.47	$51.45	$51.50
7 purchase totals =	$901.59		$975.1000	$975.10	$975.05	$975.00