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	$93.69	8.294%	$101.4606	$101.46	$101.45	$101.50
Purchase #2	$146.32	6.419%	$155.7123	$155.71	$155.70	$155.70
Purchase #3	$87.47	3.652%	$90.6644	$90.66	$90.65	$90.70
Purchase #4	$180.66	9.847%	$198.4496	$198.45	$198.45	$198.40
Purchase #5	$178.65	9.712%	$196.0005	$196.00	$196.00	$196.00
Purchase #6	$43.89	12.550%	$49.3982	$49.40	$49.40	$49.40
Purchase #7	$83.82	11.644%	$93.58	$93.58	$93.60	$93.60
7 purchase totals =	$814.50		$885.2656	$885.26	$885.25	$885.30