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	$186.35	5.436%	$196.48	$196.48	$196.50	$196.50
Purchase #2	$11.50	9.633%	$12.6078	$12.61	$12.60	$12.60
Purchase #3	$184.87	5.191%	$194.4666	$194.47	$194.45	$194.50
Purchase #4	$23.94	13.181%	$27.0955	$27.10	$27.10	$27.10
Purchase #5	$170.95	11.250%	$190.1819	$190.18	$190.20	$190.20
Purchase #6	$107.61	7.563%	$115.7485	$115.75	$115.75	$115.70
Purchase #7	$235.42	13.241%	$266.592	$266.59	$266.60	$266.60
7 purchase totals =	$920.64		$1,003.1723	$1,003.18	$1,003.20	$1,003.20