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	$183.61	9.377%	$200.8271	$200.83	$200.85	$200.80
Purchase #2	$97.82	6.778%	$104.4502	$104.45	$104.45	$104.50
Purchase #3	$100.34	5.549%	$105.9079	$105.91	$105.90	$105.90
Purchase #4	$200.95	12.653%	$226.3762	$226.38	$226.40	$226.40
Purchase #5	$216.99	13.823%	$246.9845	$246.98	$247.00	$247.00
Purchase #6	$90.54	10.789%	$100.3084	$100.31	$100.30	$100.30
Purchase #7	$199.73	7.564%	$214.8376	$214.84	$214.85	$214.80
7 purchase totals =	$1,089.98		$1,199.6919	$1,199.70	$1,199.75	$1,199.70