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	$189.79	13.643%	$215.683	$215.68	$215.70	$215.70
Purchase #2	$192.89	12.778%	$217.5375	$217.54	$217.55	$217.50
Purchase #3	$14.53	9.162%	$15.8612	$15.86	$15.85	$15.90
Purchase #4	$101.49	9.833%	$111.4695	$111.47	$111.45	$111.50
Purchase #5	$127.44	10.469%	$140.7817	$140.78	$140.80	$140.80
Purchase #6	$184.35	4.532%	$192.7047	$192.70	$192.70	$192.70
Purchase #7	$184.50	3.131%	$190.2767	$190.28	$190.30	$190.30
7 purchase totals =	$994.99		$1,084.3143	$1,084.31	$1,084.35	$1,084.40