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	$16.51	6.327%	$17.5546	$17.55	$17.55	$17.60
Purchase #2	$176.89	10.854%	$196.0896	$196.09	$196.10	$196.10
Purchase #3	$102.53	10.139%	$112.9255	$112.93	$112.95	$112.90
Purchase #4	$94.29	6.604%	$100.5169	$100.52	$100.50	$100.50
Purchase #5	$48.29	10.770%	$53.4908	$53.49	$53.50	$53.50
Purchase #6	$175.29	10.270%	$193.2923	$193.29	$193.30	$193.30
Purchase #7	$200.89	9.670%	$220.3161	$220.32	$220.30	$220.30
7 purchase totals =	$814.69		$894.1858	$894.19	$894.20	$894.20