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	$189.89	13.345%	$215.2308	$215.23	$215.25	$215.20
Purchase #2	$210.29	13.234%	$238.1198	$238.12	$238.10	$238.10
Purchase #3	$60.56	5.327%	$63.786	$63.79	$63.80	$63.80
Purchase #4	$17.89	10.568%	$19.7806	$19.78	$19.80	$19.80
Purchase #5	$117.39	10.806%	$130.0752	$130.08	$130.10	$130.10
Purchase #6	$114.47	11.138%	$127.2197	$127.22	$127.20	$127.20
Purchase #7	$192.50	11.872%	$215.3536	$215.35	$215.35	$215.40
7 purchase totals =	$902.99		$1,009.5657	$1,009.57	$1,009.60	$1,009.60