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	$132.26	9.736%	$145.1368	$145.14	$145.15	$145.10
Purchase #2	$40.94	12.777%	$46.1709	$46.17	$46.15	$46.20
Purchase #3	$184.81	6.144%	$196.1647	$196.16	$196.15	$196.20
Purchase #4	$122.40	4.248%	$127.5996	$127.60	$127.60	$127.60
Purchase #5	$90.70	8.783%	$98.6662	$98.67	$98.65	$98.70
Purchase #6	$89.32	5.304%	$94.0575	$94.06	$94.05	$94.10
Purchase #7	$184.59	8.295%	$199.9017	$199.90	$199.90	$199.90
7 purchase totals =	$845.02		$907.6974	$907.70	$907.65	$907.80