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	$34.66	10.472%	$38.2896	$38.29	$38.30	$38.30
Purchase #2	$114.44	7.695%	$123.2462	$123.25	$123.25	$123.20
Purchase #3	$9.58	13.563%	$10.8793	$10.88	$10.90	$10.90
Purchase #4	$212.58	8.254%	$230.1264	$230.13	$230.15	$230.10
Purchase #5	$132.89	11.784%	$148.5498	$148.55	$148.55	$148.50
Purchase #6	$167.95	9.287%	$183.5475	$183.55	$183.55	$183.50
Purchase #7	$240.63	12.601%	$270.9518	$270.95	$270.95	$271.00
7 purchase totals =	$912.73		$1,005.5906	$1,005.60	$1,005.65	$1,005.50