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	$127.98	10.583%	$141.5241	$141.52	$141.50	$141.50
Purchase #2	$92.84	11.237%	$103.2724	$103.27	$103.25	$103.30
Purchase #3	$8.98	9.614%	$9.8433	$9.84	$9.85	$9.80
Purchase #4	$165.56	9.474%	$181.2452	$181.25	$181.25	$181.20
Purchase #5	$104.72	11.285%	$116.5377	$116.54	$116.55	$116.50
Purchase #6	$35.70	3.131%	$36.8178	$36.82	$36.80	$36.80
Purchase #7	$99.45	12.548%	$111.929	$111.93	$111.95	$111.90
7 purchase totals =	$635.23		$701.1695	$701.17	$701.15	$701.00