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	$101.70	12.708%	$114.624	$114.62	$114.60	$114.60
Purchase #2	$15.39	12.211%	$17.2693	$17.27	$17.25	$17.30
Purchase #3	$192.41	10.298%	$212.2244	$212.22	$212.20	$212.20
Purchase #4	$140.57	12.516%	$158.1637	$158.16	$158.15	$158.20
Purchase #5	$91.55	13.295%	$103.7216	$103.72	$103.70	$103.70
Purchase #6	$89.42	11.215%	$99.4485	$99.45	$99.45	$99.40
Purchase #7	$114.49	11.264%	$127.3862	$127.39	$127.40	$127.40
7 purchase totals =	$745.53		$832.8377	$832.83	$832.75	$832.80