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	$138.50	3.279%	$143.0414	$143.04	$143.05	$143.00
Purchase #2	$98.93	7.295%	$106.1469	$106.15	$106.15	$106.10
Purchase #3	$218.69	13.264%	$247.697	$247.70	$247.70	$247.70
Purchase #4	$65.31	10.472%	$72.1493	$72.15	$72.15	$72.10
Purchase #5	$155.31	4.712%	$162.6282	$162.63	$162.65	$162.60
Purchase #6	$31.65	9.342%	$34.6067	$34.61	$34.60	$34.60
Purchase #7	$220.30	9.518%	$241.2682	$241.27	$241.25	$241.30
7 purchase totals =	$928.69		$1,007.5377	$1,007.55	$1,007.55	$1,007.40