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	$141.69	6.873%	$151.4284	$151.43	$151.45	$151.40
Purchase #2	$198.61	3.529%	$205.6189	$205.62	$205.60	$205.60
Purchase #3	$129.72	9.622%	$142.2017	$142.20	$142.20	$142.20
Purchase #4	$113.61	8.832%	$123.644	$123.64	$123.65	$123.60
Purchase #5	$205.50	6.375%	$218.6006	$218.60	$218.60	$218.60
Purchase #6	$67.61	6.330%	$71.8897	$71.89	$71.90	$71.90
Purchase #7	$49.95	4.624%	$52.2597	$52.26	$52.25	$52.30
7 purchase totals =	$906.69		$965.6430	$965.64	$965.65	$965.60