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	$37.47	11.176%	$41.6576	$41.66	$41.65	$41.70
Purchase #2	$146.78	9.740%	$161.0764	$161.08	$161.10	$161.10
Purchase #3	$98.45	13.315%	$111.5586	$111.56	$111.55	$111.60
Purchase #4	$65.45	10.495%	$72.319	$72.32	$72.30	$72.30
Purchase #5	$231.66	6.424%	$246.5418	$246.54	$246.55	$246.50
Purchase #6	$182.53	5.255%	$192.122	$192.12	$192.10	$192.10
Purchase #7	$231.58	13.266%	$262.3014	$262.30	$262.30	$262.30
7 purchase totals =	$993.92		$1,087.5768	$1,087.58	$1,087.55	$1,087.60