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	$82.71	4.288%	$86.2566	$86.26	$86.25	$86.30
Purchase #2	$250.45	9.162%	$273.3962	$273.40	$273.40	$273.40
Purchase #3	$148.79	6.204%	$158.0209	$158.02	$158.00	$158.00
Purchase #4	$73.46	12.295%	$82.4919	$82.49	$82.50	$82.50
Purchase #5	$161.92	12.143%	$181.5819	$181.58	$181.60	$181.60
Purchase #6	$214.48	13.175%	$242.7377	$242.74	$242.75	$242.70
Purchase #7	$90.46	10.530%	$99.9854	$99.99	$100.00	$100.00
7 purchase totals =	$1,022.27		$1,124.4706	$1,124.48	$1,124.50	$1,124.50