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	$48.58	11.393%	$54.1147	$54.11	$54.10	$54.10
Purchase #2	$38.28	9.280%	$41.8324	$41.83	$41.85	$41.80
Purchase #3	$240.29	6.396%	$255.6589	$255.66	$255.65	$255.70
Purchase #4	$164.61	10.739%	$182.2875	$182.29	$182.30	$182.30
Purchase #5	$9.42	7.197%	$10.098	$10.10	$10.10	$10.10
Purchase #6	$142.81	13.733%	$162.4221	$162.42	$162.40	$162.40
Purchase #7	$99.67	4.328%	$103.9837	$103.98	$104.00	$104.00
7 purchase totals =	$743.66		$810.3973	$810.39	$810.40	$810.40