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	$100.56	9.136%	$109.7472	$109.75	$109.75	$109.70
Purchase #2	$119.62	6.392%	$127.2661	$127.27	$127.25	$127.30
Purchase #3	$49.89	6.133%	$52.9498	$52.95	$52.95	$52.90
Purchase #4	$71.54	4.458%	$74.7293	$74.73	$74.75	$74.70
Purchase #5	$40.32	6.727%	$43.0323	$43.03	$43.05	$43.00
Purchase #6	$74.87	5.333%	$78.8628	$78.86	$78.85	$78.90
Purchase #7	$175.49	3.281%	$181.2478	$181.25	$181.25	$181.20
7 purchase totals =	$632.29		$667.8353	$667.84	$667.85	$667.70