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	$227.83	11.741%	$254.5795	$254.58	$254.60	$254.60
Purchase #2	$184.48	12.312%	$207.1932	$207.19	$207.20	$207.20
Purchase #3	$50.94	12.117%	$57.1124	$57.11	$57.10	$57.10
Purchase #4	$49.79	3.395%	$51.4804	$51.48	$51.50	$51.50
Purchase #5	$103.58	10.509%	$114.4652	$114.47	$114.45	$114.50
Purchase #6	$72.99	13.174%	$82.6057	$82.61	$82.60	$82.60
Purchase #7	$98.49	11.559%	$109.8745	$109.87	$109.85	$109.90
7 purchase totals =	$788.10		$877.3109	$877.31	$877.30	$877.40