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	$200.71	11.303%	$223.3963	$223.40	$223.40	$223.40
Purchase #2	$90.65	10.418%	$100.0939	$100.09	$100.10	$100.10
Purchase #3	$155.70	9.120%	$169.8998	$169.90	$169.90	$169.90
Purchase #4	$15.71	12.431%	$17.6629	$17.66	$17.65	$17.70
Purchase #5	$72.44	8.187%	$78.3707	$78.37	$78.35	$78.40
Purchase #6	$226.42	11.690%	$252.8885	$252.89	$252.90	$252.90
Purchase #7	$30.84	12.112%	$34.5753	$34.58	$34.60	$34.60
7 purchase totals =	$792.47		$876.8874	$876.89	$876.90	$877.00