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	$161.28	13.346%	$182.8044	$182.80	$182.80	$182.80
Purchase #2	$85.40	4.396%	$89.1542	$89.15	$89.15	$89.20
Purchase #3	$242.35	12.163%	$271.827	$271.83	$271.85	$271.80
Purchase #4	$13.35	3.294%	$13.7897	$13.79	$13.80	$13.80
Purchase #5	$129.84	10.534%	$143.5173	$143.52	$143.50	$143.50
Purchase #6	$147.59	10.384%	$162.9157	$162.92	$162.90	$162.90
Purchase #7	$108.80	5.340%	$114.6099	$114.61	$114.60	$114.60
7 purchase totals =	$888.61		$978.6182	$978.62	$978.60	$978.60