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	$101.30	7.689%	$109.089	$109.09	$109.10	$109.10
Purchase #2	$158.99	3.514%	$164.5769	$164.58	$164.60	$164.60
Purchase #3	$192.62	8.134%	$208.2877	$208.29	$208.30	$208.30
Purchase #4	$224.65	8.305%	$243.3072	$243.31	$243.30	$243.30
Purchase #5	$62.67	6.565%	$66.7843	$66.78	$66.80	$66.80
Purchase #6	$180.40	5.143%	$189.678	$189.68	$189.70	$189.70
Purchase #7	$33.53	13.630%	$38.1001	$38.10	$38.10	$38.10
7 purchase totals =	$954.16		$1,019.8232	$1,019.83	$1,019.90	$1,019.90