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	$215.36	6.737%	$229.8688	$229.87	$229.85	$229.90
Purchase #2	$184.36	13.532%	$209.3076	$209.31	$209.30	$209.30
Purchase #3	$230.52	4.259%	$240.3378	$240.34	$240.35	$240.30
Purchase #4	$241.71	6.283%	$256.8966	$256.90	$256.90	$256.90
Purchase #5	$55.39	7.603%	$59.6013	$59.60	$59.60	$59.60
Purchase #6	$122.94	11.513%	$137.0941	$137.09	$137.10	$137.10
Purchase #7	$43.42	13.666%	$49.3538	$49.35	$49.35	$49.40
7 purchase totals =	$1,093.70		$1,182.4600	$1,182.46	$1,182.45	$1,182.50