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	$217.52	3.622%	$225.3986	$225.40	$225.40	$225.40
Purchase #2	$116.87	13.857%	$133.0647	$133.06	$133.05	$133.10
Purchase #3	$135.98	11.121%	$151.1023	$151.10	$151.10	$151.10
Purchase #4	$64.39	11.693%	$71.9191	$71.92	$71.90	$71.90
Purchase #5	$114.96	11.822%	$128.5506	$128.55	$128.55	$128.60
Purchase #6	$178.96	10.589%	$197.9101	$197.91	$197.90	$197.90
Purchase #7	$136.77	12.361%	$153.6761	$153.68	$153.70	$153.70
7 purchase totals =	$965.45		$1,061.6215	$1,061.62	$1,061.60	$1,061.70