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	$136.76	10.436%	$151.0323	$151.03	$151.05	$151.00
Purchase #2	$23.29	13.130%	$26.348	$26.35	$26.35	$26.30
Purchase #3	$205.32	12.537%	$231.061	$231.06	$231.05	$231.10
Purchase #4	$35.60	5.103%	$37.4167	$37.42	$37.40	$37.40
Purchase #5	$90.63	10.620%	$100.2549	$100.25	$100.25	$100.30
Purchase #6	$157.85	9.156%	$172.3027	$172.30	$172.30	$172.30
Purchase #7	$130.62	8.304%	$141.4667	$141.47	$141.45	$141.50
7 purchase totals =	$780.07		$859.8823	$859.88	$859.85	$859.90