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	$242.60	8.119%	$262.2967	$262.30	$262.30	$262.30
Purchase #2	$64.60	11.683%	$72.1472	$72.15	$72.15	$72.10
Purchase #3	$90.47	13.825%	$102.9775	$102.98	$103.00	$103.00
Purchase #4	$158.95	5.577%	$167.8146	$167.81	$167.80	$167.80
Purchase #5	$143.30	5.301%	$150.8963	$150.90	$150.90	$150.90
Purchase #6	$216.90	4.495%	$226.6497	$226.65	$226.65	$226.60
Purchase #7	$78.53	13.320%	$88.9902	$88.99	$89.00	$89.00
7 purchase totals =	$995.35		$1,071.7722	$1,071.78	$1,071.80	$1,071.70