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	$194.49	5.683%	$205.5429	$205.54	$205.55	$205.50
Purchase #2	$225.48	13.337%	$255.5523	$255.55	$255.55	$255.60
Purchase #3	$99.66	12.245%	$111.8634	$111.86	$111.85	$111.90
Purchase #4	$104.33	11.475%	$116.3019	$116.30	$116.30	$116.30
Purchase #5	$242.42	13.164%	$274.3322	$274.33	$274.35	$274.30
Purchase #6	$9.77	9.450%	$10.6933	$10.69	$10.70	$10.70
Purchase #7	$95.60	6.693%	$101.9985	$102.00	$102.00	$102.00
7 purchase totals =	$971.75		$1,076.2845	$1,076.27	$1,076.30	$1,076.30