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	$183.96	13.784%	$209.317	$209.32	$209.30	$209.30
Purchase #2	$98.73	5.186%	$103.8501	$103.85	$103.85	$103.90
Purchase #3	$164.73	7.739%	$177.4785	$177.48	$177.50	$177.50
Purchase #4	$50.86	10.632%	$56.2674	$56.27	$56.25	$56.30
Purchase #5	$127.45	13.802%	$145.0406	$145.04	$145.05	$145.00
Purchase #6	$176.69	5.619%	$186.6182	$186.62	$186.60	$186.60
Purchase #7	$170.96	13.172%	$193.4789	$193.48	$193.50	$193.50
7 purchase totals =	$973.38		$1,072.0507	$1,072.06	$1,072.05	$1,072.10