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	$38.26	13.737%	$43.5158	$43.52	$43.50	$43.50
Purchase #2	$179.35	7.193%	$192.2506	$192.25	$192.25	$192.30
Purchase #3	$131.64	10.794%	$145.8492	$145.85	$145.85	$145.80
Purchase #4	$234.76	8.809%	$255.44	$255.44	$255.45	$255.40
Purchase #5	$216.94	12.466%	$243.9837	$243.98	$244.00	$244.00
Purchase #6	$43.93	5.225%	$46.2253	$46.23	$46.25	$46.20
Purchase #7	$92.68	10.712%	$102.6079	$102.61	$102.60	$102.60
7 purchase totals =	$937.56		$1,029.8725	$1,029.88	$1,029.90	$1,029.80