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	$127.70	12.499%	$143.6612	$143.66	$143.65	$143.70
Purchase #2	$136.29	11.169%	$151.5122	$151.51	$151.50	$151.50
Purchase #3	$169.90	6.603%	$181.1185	$181.12	$181.10	$181.10
Purchase #4	$134.71	3.853%	$139.9004	$139.90	$139.90	$139.90
Purchase #5	$96.75	4.272%	$100.8832	$100.88	$100.90	$100.90
Purchase #6	$124.47	8.141%	$134.6031	$134.60	$134.60	$134.60
Purchase #7	$144.61	3.445%	$149.5918	$149.59	$149.60	$149.60
7 purchase totals =	$934.43		$1,001.2704	$1,001.26	$1,001.25	$1,001.30