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	$20.71	10.212%	$22.8249	$22.82	$22.80	$22.80
Purchase #2	$239.31	3.862%	$248.5522	$248.55	$248.55	$248.60
Purchase #3	$232.85	12.681%	$262.3777	$262.38	$262.40	$262.40
Purchase #4	$127.84	3.725%	$132.602	$132.60	$132.60	$132.60
Purchase #5	$41.66	5.276%	$43.858	$43.86	$43.85	$43.90
Purchase #6	$153.61	8.626%	$166.8604	$166.86	$166.85	$166.90
Purchase #7	$146.29	6.335%	$155.5575	$155.56	$155.55	$155.60
7 purchase totals =	$962.27		$1,032.6327	$1,032.63	$1,032.60	$1,032.80