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	$95.93	11.574%	$107.0329	$107.03	$107.05	$107.00
Purchase #2	$19.30	12.730%	$21.7569	$21.76	$21.75	$21.80
Purchase #3	$18.69	9.762%	$20.5145	$20.51	$20.50	$20.50
Purchase #4	$105.43	5.693%	$111.4321	$111.43	$111.45	$111.40
Purchase #5	$166.53	11.824%	$186.2205	$186.22	$186.20	$186.20
Purchase #6	$152.61	12.409%	$171.5474	$171.55	$171.55	$171.50
Purchase #7	$121.25	11.868%	$135.64	$135.64	$135.65	$135.60
7 purchase totals =	$679.74		$754.1443	$754.14	$754.15	$754.00