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	$94.88	11.563%	$105.851	$105.85	$105.85	$105.90
Purchase #2	$96.93	5.320%	$102.0867	$102.09	$102.10	$102.10
Purchase #3	$93.75	10.282%	$103.3894	$103.39	$103.40	$103.40
Purchase #4	$230.39	8.504%	$249.9824	$249.98	$250.00	$250.00
Purchase #5	$78.92	6.402%	$83.9725	$83.97	$83.95	$84.00
Purchase #6	$210.28	10.144%	$231.6108	$231.61	$231.60	$231.60
Purchase #7	$72.45	4.801%	$75.9283	$75.93	$75.95	$75.90
7 purchase totals =	$877.60		$952.8211	$952.82	$952.85	$952.90