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	$59.71	8.609%	$64.8504	$64.85	$64.85	$64.90
Purchase #2	$102.71	3.306%	$106.1056	$106.11	$106.10	$106.10
Purchase #3	$94.78	6.257%	$100.7104	$100.71	$100.70	$100.70
Purchase #4	$10.88	4.324%	$11.3505	$11.35	$11.35	$11.40
Purchase #5	$215.33	10.756%	$238.4909	$238.49	$238.50	$238.50
Purchase #6	$138.32	6.667%	$147.5418	$147.54	$147.55	$147.50
Purchase #7	$183.85	6.719%	$196.2029	$196.20	$196.20	$196.20
7 purchase totals =	$805.58		$865.2525	$865.25	$865.25	$865.30