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	$186.58	11.779%	$208.5573	$208.56	$208.55	$208.60
Purchase #2	$122.49	8.500%	$132.9017	$132.90	$132.90	$132.90
Purchase #3	$99.72	5.326%	$105.0311	$105.03	$105.05	$105.00
Purchase #4	$223.49	3.606%	$231.549	$231.55	$231.55	$231.50
Purchase #5	$158.64	3.418%	$164.0623	$164.06	$164.05	$164.10
Purchase #6	$147.51	6.386%	$156.93	$156.93	$156.95	$156.90
Purchase #7	$126.55	4.622%	$132.3991	$132.40	$132.40	$132.40
7 purchase totals =	$1,064.98		$1,131.4305	$1,131.43	$1,131.45	$1,131.40