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	$65.89	12.235%	$73.9516	$73.95	$73.95	$74.00
Purchase #2	$246.50	4.210%	$256.8777	$256.88	$256.90	$256.90
Purchase #3	$39.95	7.279%	$42.858	$42.86	$42.85	$42.90
Purchase #4	$41.97	9.326%	$45.8841	$45.88	$45.90	$45.90
Purchase #5	$66.79	7.723%	$71.9482	$71.95	$71.95	$71.90
Purchase #6	$12.35	10.492%	$13.6458	$13.65	$13.65	$13.60
Purchase #7	$100.25	7.335%	$107.6033	$107.60	$107.60	$107.60
7 purchase totals =	$573.70		$612.7687	$612.77	$612.80	$612.80