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	$136.45	13.257%	$154.5392	$154.54	$154.55	$154.50
Purchase #2	$127.38	13.601%	$144.705	$144.71	$144.70	$144.70
Purchase #3	$139.60	10.113%	$153.7177	$153.72	$153.70	$153.70
Purchase #4	$224.83	13.318%	$254.7729	$254.77	$254.75	$254.80
Purchase #5	$103.38	8.766%	$112.4423	$112.44	$112.45	$112.40
Purchase #6	$152.54	13.663%	$173.3815	$173.38	$173.40	$173.40
Purchase #7	$125.59	11.503%	$140.0366	$140.04	$140.05	$140.00
7 purchase totals =	$1,009.77		$1,133.5952	$1,133.60	$1,133.60	$1,133.50