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	$114.30	11.189%	$127.089	$127.09	$127.10	$127.10
Purchase #2	$26.81	10.543%	$29.6366	$29.64	$29.65	$29.60
Purchase #3	$183.32	13.441%	$207.96	$207.96	$207.95	$208.00
Purchase #4	$246.73	11.154%	$274.2503	$274.25	$274.25	$274.30
Purchase #5	$80.45	11.691%	$89.8554	$89.86	$89.85	$89.90
Purchase #6	$77.35	10.557%	$85.5158	$85.52	$85.50	$85.50
Purchase #7	$111.87	5.584%	$118.1168	$118.12	$118.10	$118.10
7 purchase totals =	$840.83		$932.4239	$932.44	$932.40	$932.50