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	$153.82	12.126%	$172.4722	$172.47	$172.45	$172.50
Purchase #2	$43.69	13.778%	$49.7096	$49.71	$49.70	$49.70
Purchase #3	$96.31	4.597%	$100.7374	$100.74	$100.75	$100.70
Purchase #4	$134.52	5.792%	$142.3114	$142.31	$142.30	$142.30
Purchase #5	$122.70	13.229%	$138.932	$138.93	$138.95	$138.90
Purchase #6	$87.72	4.123%	$91.3367	$91.34	$91.35	$91.30
Purchase #7	$230.31	10.442%	$254.359	$254.36	$254.35	$254.40
7 purchase totals =	$869.07		$949.8583	$949.86	$949.85	$949.80