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	$246.41	11.178%	$273.9537	$273.95	$273.95	$274.00
Purchase #2	$134.43	12.399%	$151.098	$151.10	$151.10	$151.10
Purchase #3	$31.89	8.498%	$34.6	$34.60	$34.60	$34.60
Purchase #4	$127.86	5.184%	$134.4883	$134.49	$134.50	$134.50
Purchase #5	$219.98	8.530%	$238.7443	$238.74	$238.75	$238.70
Purchase #6	$199.74	10.858%	$221.4278	$221.43	$221.45	$221.40
Purchase #7	$44.96	10.427%	$49.648	$49.65	$49.65	$49.60
7 purchase totals =	$1,005.27		$1,103.9601	$1,103.96	$1,104.00	$1,103.90