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	$24.53	4.555%	$25.6473	$25.65	$25.65	$25.60
Purchase #2	$241.67	12.393%	$271.6202	$271.62	$271.60	$271.60
Purchase #3	$230.39	13.254%	$260.9259	$260.93	$260.95	$260.90
Purchase #4	$242.26	13.693%	$275.4327	$275.43	$275.45	$275.40
Purchase #5	$56.81	5.403%	$59.8794	$59.88	$59.90	$59.90
Purchase #6	$193.31	10.145%	$212.9213	$212.92	$212.90	$212.90
Purchase #7	$34.97	6.784%	$37.3424	$37.34	$37.35	$37.30
7 purchase totals =	$1,023.94		$1,143.7692	$1,143.77	$1,143.80	$1,143.60