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	$86.30	12.176%	$96.8079	$96.81	$96.80	$96.80
Purchase #2	$28.89	9.778%	$31.7149	$31.71	$31.70	$31.70
Purchase #3	$244.94	4.720%	$256.5012	$256.50	$256.50	$256.50
Purchase #4	$147.90	7.116%	$158.4246	$158.42	$158.40	$158.40
Purchase #5	$174.57	12.810%	$196.9324	$196.93	$196.95	$196.90
Purchase #6	$212.60	7.769%	$229.1169	$229.12	$229.10	$229.10
Purchase #7	$21.27	8.119%	$22.9969	$23.00	$23.00	$23.00
7 purchase totals =	$916.47		$992.4948	$992.49	$992.45	$992.40