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	$126.76	13.604%	$144.0044	$144.00	$144.00	$144.00
Purchase #2	$78.90	13.478%	$89.5341	$89.53	$89.55	$89.50
Purchase #3	$12.39	9.803%	$13.6046	$13.60	$13.60	$13.60
Purchase #4	$65.45	11.162%	$72.7555	$72.76	$72.75	$72.80
Purchase #5	$14.96	8.146%	$16.1786	$16.18	$16.20	$16.20
Purchase #6	$126.30	4.825%	$132.394	$132.39	$132.40	$132.40
Purchase #7	$90.68	8.405%	$98.3017	$98.30	$98.30	$98.30
7 purchase totals =	$515.44		$566.7729	$566.76	$566.80	$566.80