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	$117.98	12.322%	$132.5175	$132.52	$132.50	$132.50
Purchase #2	$107.78	7.580%	$115.9497	$115.95	$115.95	$115.90
Purchase #3	$64.53	4.712%	$67.5707	$67.57	$67.55	$67.60
Purchase #4	$150.81	3.482%	$156.0612	$156.06	$156.05	$156.10
Purchase #5	$62.61	10.313%	$69.067	$69.07	$69.05	$69.10
Purchase #6	$233.53	10.721%	$258.5668	$258.57	$258.55	$258.60
Purchase #7	$238.89	7.123%	$255.9061	$255.91	$255.90	$255.90
7 purchase totals =	$976.13		$1,055.6390	$1,055.65	$1,055.55	$1,055.70