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	$208.55	8.198%	$225.6469	$225.65	$225.65	$225.60
Purchase #2	$28.80	4.826%	$30.1899	$30.19	$30.20	$30.20
Purchase #3	$111.68	4.139%	$116.3024	$116.30	$116.30	$116.30
Purchase #4	$102.39	8.783%	$111.3829	$111.38	$111.40	$111.40
Purchase #5	$62.25	12.178%	$69.8308	$69.83	$69.85	$69.80
Purchase #6	$209.83	11.777%	$234.5417	$234.54	$234.55	$234.50
Purchase #7	$228.83	12.133%	$256.5939	$256.59	$256.60	$256.60
7 purchase totals =	$952.33		$1,044.4885	$1,044.48	$1,044.55	$1,044.40