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	$239.66	6.695%	$255.7052	$255.71	$255.70	$255.70
Purchase #2	$110.74	5.104%	$116.3922	$116.39	$116.40	$116.40
Purchase #3	$225.94	6.481%	$240.5832	$240.58	$240.60	$240.60
Purchase #4	$80.42	10.446%	$88.8207	$88.82	$88.80	$88.80
Purchase #5	$142.81	6.140%	$151.5785	$151.58	$151.60	$151.60
Purchase #6	$60.88	7.491%	$65.4405	$65.44	$65.45	$65.40
Purchase #7	$106.38	10.433%	$117.4786	$117.48	$117.50	$117.50
7 purchase totals =	$966.83		$1,035.9989	$1,036.00	$1,036.05	$1,036.00