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	$227.70	11.456%	$253.7853	$253.79	$253.80	$253.80
Purchase #2	$210.65	5.307%	$221.8292	$221.83	$221.85	$221.80
Purchase #3	$237.45	11.861%	$265.6139	$265.61	$265.60	$265.60
Purchase #4	$66.71	8.541%	$72.4077	$72.41	$72.40	$72.40
Purchase #5	$6.85	6.841%	$7.3186	$7.32	$7.30	$7.30
Purchase #6	$194.74	5.210%	$204.886	$204.89	$204.90	$204.90
Purchase #7	$18.39	5.523%	$19.4057	$19.41	$19.40	$19.40
7 purchase totals =	$962.49		$1,045.2464	$1,045.26	$1,045.25	$1,045.20