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	$95.65	12.819%	$107.9114	$107.91	$107.90	$107.90
Purchase #2	$127.68	6.113%	$135.4851	$135.49	$135.50	$135.50
Purchase #3	$56.89	4.283%	$59.3266	$59.33	$59.35	$59.30
Purchase #4	$43.42	5.196%	$45.6761	$45.68	$45.70	$45.70
Purchase #5	$195.51	9.725%	$214.5233	$214.52	$214.50	$214.50
Purchase #6	$139.87	6.250%	$148.6119	$148.61	$148.60	$148.60
Purchase #7	$78.55	12.193%	$88.1276	$88.13	$88.15	$88.10
7 purchase totals =	$737.57		$799.6620	$799.67	$799.70	$799.60