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	$69.32	10.447%	$76.5619	$76.56	$76.55	$76.60
Purchase #2	$226.76	13.129%	$256.5313	$256.53	$256.55	$256.50
Purchase #3	$113.34	4.868%	$118.8574	$118.86	$118.85	$118.90
Purchase #4	$9.60	12.278%	$10.7787	$10.78	$10.80	$10.80
Purchase #5	$78.30	8.842%	$85.2233	$85.22	$85.20	$85.20
Purchase #6	$159.39	12.555%	$179.4014	$179.40	$179.40	$179.40
Purchase #7	$248.42	9.332%	$271.6026	$271.60	$271.60	$271.60
7 purchase totals =	$905.13		$998.9566	$998.95	$998.95	$999.00