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	$100.56	4.322%	$104.9062	$104.91	$104.90	$104.90
Purchase #2	$16.67	4.536%	$17.4262	$17.43	$17.45	$17.40
Purchase #3	$222.35	4.140%	$231.5553	$231.56	$231.55	$231.60
Purchase #4	$162.65	7.140%	$174.2632	$174.26	$174.25	$174.30
Purchase #5	$225.77	13.239%	$255.6597	$255.66	$255.65	$255.70
Purchase #6	$170.28	8.835%	$185.3242	$185.32	$185.30	$185.30
Purchase #7	$48.48	6.667%	$51.7122	$51.71	$51.70	$51.70
7 purchase totals =	$946.76		$1,020.8470	$1,020.85	$1,020.80	$1,020.90