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	$31.79	6.695%	$33.9183	$33.92	$33.90	$33.90
Purchase #2	$172.50	13.678%	$196.0946	$196.09	$196.10	$196.10
Purchase #3	$190.41	7.681%	$205.0354	$205.04	$205.05	$205.00
Purchase #4	$174.60	12.209%	$195.9169	$195.92	$195.90	$195.90
Purchase #5	$53.86	7.144%	$57.7078	$57.71	$57.70	$57.70
Purchase #6	$97.53	11.296%	$108.547	$108.55	$108.55	$108.50
Purchase #7	$222.79	7.106%	$238.6215	$238.62	$238.60	$238.60
7 purchase totals =	$943.48		$1,035.8415	$1,035.85	$1,035.80	$1,035.70