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	$118.29	3.114%	$121.9736	$121.97	$121.95	$122.00
Purchase #2	$126.53	12.218%	$141.9894	$141.99	$142.00	$142.00
Purchase #3	$11.74	7.476%	$12.6177	$12.62	$12.60	$12.60
Purchase #4	$152.31	12.491%	$171.335	$171.34	$171.35	$171.30
Purchase #5	$86.44	13.827%	$98.3921	$98.39	$98.40	$98.40
Purchase #6	$45.52	11.138%	$50.59	$50.59	$50.60	$50.60
Purchase #7	$38.75	9.868%	$42.5739	$42.57	$42.55	$42.60
7 purchase totals =	$579.58		$639.4717	$639.47	$639.45	$639.50