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	$33.47	11.603%	$37.3535	$37.35	$37.35	$37.40
Purchase #2	$107.54	3.553%	$111.3609	$111.36	$111.35	$111.40
Purchase #3	$60.84	7.106%	$65.1633	$65.16	$65.15	$65.20
Purchase #4	$74.36	5.406%	$78.3799	$78.38	$78.40	$78.40
Purchase #5	$45.70	12.158%	$51.2562	$51.26	$51.25	$51.30
Purchase #6	$123.35	7.480%	$132.5766	$132.58	$132.60	$132.60
Purchase #7	$76.29	6.351%	$81.1352	$81.14	$81.15	$81.10
7 purchase totals =	$521.55		$557.2256	$557.23	$557.25	$557.40