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	$176.84	13.145%	$200.0856	$200.09	$200.10	$200.10
Purchase #2	$77.52	13.361%	$87.8774	$87.88	$87.90	$87.90
Purchase #3	$77.59	3.578%	$80.3662	$80.37	$80.35	$80.40
Purchase #4	$215.70	6.593%	$229.9211	$229.92	$229.90	$229.90
Purchase #5	$78.59	11.693%	$87.7795	$87.78	$87.80	$87.80
Purchase #6	$219.93	13.194%	$248.9476	$248.95	$248.95	$248.90
Purchase #7	$25.93	7.567%	$27.8921	$27.89	$27.90	$27.90
7 purchase totals =	$872.10		$962.8695	$962.88	$962.90	$962.90