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	$163.65	10.132%	$180.231	$180.23	$180.25	$180.20
Purchase #2	$157.51	5.298%	$165.8549	$165.85	$165.85	$165.90
Purchase #3	$109.26	10.175%	$120.3772	$120.38	$120.40	$120.40
Purchase #4	$140.35	8.162%	$151.8054	$151.81	$151.80	$151.80
Purchase #5	$134.39	9.247%	$146.817	$146.82	$146.80	$146.80
Purchase #6	$183.26	3.872%	$190.3558	$190.36	$190.35	$190.40
Purchase #7	$73.60	13.439%	$83.4911	$83.49	$83.50	$83.50
7 purchase totals =	$962.02		$1,038.9324	$1,038.94	$1,038.95	$1,039.00