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	$134.94	7.158%	$144.599	$144.60	$144.60	$144.60
Purchase #2	$103.31	5.590%	$109.085	$109.09	$109.10	$109.10
Purchase #3	$62.40	9.160%	$68.1158	$68.12	$68.10	$68.10
Purchase #4	$202.81	12.666%	$228.4979	$228.50	$228.50	$228.50
Purchase #5	$119.66	6.198%	$127.0765	$127.08	$127.10	$127.10
Purchase #6	$63.74	4.372%	$66.5267	$66.53	$66.55	$66.50
Purchase #7	$108.60	13.622%	$123.3935	$123.39	$123.40	$123.40
7 purchase totals =	$795.46		$867.2944	$867.31	$867.35	$867.30