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	$56.30	9.828%	$61.8332	$61.83	$61.85	$61.80
Purchase #2	$201.80	4.540%	$210.9617	$210.96	$210.95	$211.00
Purchase #3	$244.31	4.528%	$255.3724	$255.37	$255.35	$255.40
Purchase #4	$36.94	13.428%	$41.9003	$41.90	$41.90	$41.90
Purchase #5	$158.86	3.332%	$164.1532	$164.15	$164.15	$164.20
Purchase #6	$125.32	5.189%	$131.8229	$131.82	$131.80	$131.80
Purchase #7	$45.57	10.238%	$50.2355	$50.24	$50.25	$50.20
7 purchase totals =	$869.10		$916.2792	$916.27	$916.25	$916.30