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	$216.79	11.220%	$241.1138	$241.11	$241.10	$241.10
Purchase #2	$127.62	3.621%	$132.2411	$132.24	$132.25	$132.20
Purchase #3	$128.83	6.747%	$137.5222	$137.52	$137.50	$137.50
Purchase #4	$137.29	5.169%	$144.3865	$144.39	$144.40	$144.40
Purchase #5	$127.72	13.818%	$145.3683	$145.37	$145.35	$145.40
Purchase #6	$220.42	3.104%	$227.2618	$227.26	$227.25	$227.30
Purchase #7	$145.83	5.816%	$154.3115	$154.31	$154.30	$154.30
7 purchase totals =	$1,104.50		$1,182.2052	$1,182.20	$1,182.15	$1,182.20