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	$39.93	9.379%	$43.675	$43.68	$43.70	$43.70
Purchase #2	$179.31	4.292%	$187.006	$187.01	$187.00	$187.00
Purchase #3	$61.61	8.710%	$66.9762	$66.98	$67.00	$67.00
Purchase #4	$171.43	10.610%	$189.6187	$189.62	$189.60	$189.60
Purchase #5	$134.85	11.788%	$150.7461	$150.75	$150.75	$150.70
Purchase #6	$89.66	12.115%	$100.5223	$100.52	$100.50	$100.50
Purchase #7	$230.25	8.364%	$249.5081	$249.51	$249.50	$249.50
7 purchase totals =	$907.04		$988.0524	$988.07	$988.05	$988.00