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	$138.95	8.583%	$150.8761	$150.88	$150.90	$150.90
Purchase #2	$198.86	3.161%	$205.146	$205.15	$205.15	$205.10
Purchase #3	$178.63	6.300%	$189.8837	$189.88	$189.90	$189.90
Purchase #4	$75.37	9.174%	$82.2844	$82.28	$82.30	$82.30
Purchase #5	$130.76	13.543%	$148.4688	$148.47	$148.45	$148.50
Purchase #6	$177.46	13.567%	$201.536	$201.54	$201.55	$201.50
Purchase #7	$128.53	10.376%	$141.8663	$141.87	$141.85	$141.90
7 purchase totals =	$1,028.56		$1,120.0613	$1,120.07	$1,120.10	$1,120.10