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	$217.50	5.467%	$229.3907	$229.39	$229.40	$229.40
Purchase #2	$105.41	10.319%	$116.2873	$116.29	$116.30	$116.30
Purchase #3	$158.50	5.834%	$167.7469	$167.75	$167.75	$167.70
Purchase #4	$49.69	13.615%	$56.4553	$56.46	$56.45	$56.50
Purchase #5	$31.49	10.806%	$34.8928	$34.89	$34.90	$34.90
Purchase #6	$197.61	10.261%	$217.8868	$217.89	$217.90	$217.90
Purchase #7	$11.63	3.503%	$12.0374	$12.04	$12.05	$12.00
7 purchase totals =	$771.83		$834.6972	$834.71	$834.75	$834.70