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	$153.72	12.186%	$172.4523	$172.45	$172.45	$172.50
Purchase #2	$178.47	3.281%	$184.3256	$184.33	$184.35	$184.30
Purchase #3	$238.41	11.287%	$265.3193	$265.32	$265.30	$265.30
Purchase #4	$9.97	12.142%	$11.1806	$11.18	$11.20	$11.20
Purchase #5	$102.54	5.327%	$108.0023	$108.00	$108.00	$108.00
Purchase #6	$85.63	7.236%	$91.8262	$91.83	$91.85	$91.80
Purchase #7	$100.78	3.581%	$104.3889	$104.39	$104.40	$104.40
7 purchase totals =	$869.52		$937.4952	$937.50	$937.55	$937.50