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	$212.41	5.166%	$223.3831	$223.38	$223.40	$223.40
Purchase #2	$242.48	8.575%	$263.2727	$263.27	$263.25	$263.30
Purchase #3	$31.53	10.866%	$34.956	$34.96	$34.95	$35.00
Purchase #4	$87.41	3.369%	$90.3548	$90.35	$90.35	$90.40
Purchase #5	$127.71	3.843%	$132.6179	$132.62	$132.60	$132.60
Purchase #6	$175.83	9.474%	$192.4881	$192.49	$192.50	$192.50
Purchase #7	$134.52	6.652%	$143.4683	$143.47	$143.45	$143.50
7 purchase totals =	$1,011.89		$1,080.5409	$1,080.54	$1,080.50	$1,080.70