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	$128.63	11.304%	$143.1703	$143.17	$143.15	$143.20
Purchase #2	$231.80	7.131%	$248.3297	$248.33	$248.35	$248.30
Purchase #3	$75.39	3.640%	$78.1342	$78.13	$78.15	$78.10
Purchase #4	$133.32	6.405%	$141.8591	$141.86	$141.85	$141.90
Purchase #5	$126.46	6.347%	$134.4864	$134.49	$134.50	$134.50
Purchase #6	$250.83	4.761%	$262.772	$262.77	$262.75	$262.80
Purchase #7	$239.74	9.441%	$262.3739	$262.37	$262.35	$262.40
7 purchase totals =	$1,186.17		$1,271.1256	$1,271.12	$1,271.10	$1,271.20