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	$107.86	11.124%	$119.8583	$119.86	$119.85	$119.90
Purchase #2	$200.28	10.733%	$221.7761	$221.78	$221.80	$221.80
Purchase #3	$131.39	10.685%	$145.429	$145.43	$145.45	$145.40
Purchase #4	$150.31	10.729%	$166.4368	$166.44	$166.45	$166.40
Purchase #5	$104.47	4.408%	$109.075	$109.08	$109.10	$109.10
Purchase #6	$161.86	4.274%	$168.7779	$168.78	$168.80	$168.80
Purchase #7	$198.86	5.234%	$209.2683	$209.27	$209.25	$209.30
7 purchase totals =	$1,055.03		$1,140.6214	$1,140.64	$1,140.70	$1,140.70