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	$194.30	11.866%	$217.3556	$217.36	$217.35	$217.40
Purchase #2	$70.98	3.295%	$73.3188	$73.32	$73.30	$73.30
Purchase #3	$106.85	5.182%	$112.387	$112.39	$112.40	$112.40
Purchase #4	$245.41	8.545%	$266.3803	$266.38	$266.40	$266.40
Purchase #5	$150.29	10.113%	$165.4888	$165.49	$165.50	$165.50
Purchase #6	$136.99	9.782%	$150.3904	$150.39	$150.40	$150.40
Purchase #7	$114.68	7.467%	$123.2432	$123.24	$123.25	$123.20
7 purchase totals =	$1,019.50		$1,108.5641	$1,108.57	$1,108.60	$1,108.60