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	$144.82	13.658%	$164.5995	$164.60	$164.60	$164.60
Purchase #2	$168.41	11.587%	$187.9237	$187.92	$187.90	$187.90
Purchase #3	$190.58	4.665%	$199.4706	$199.47	$199.45	$199.50
Purchase #4	$75.76	10.551%	$83.7534	$83.75	$83.75	$83.80
Purchase #5	$30.54	13.534%	$34.6733	$34.67	$34.65	$34.70
Purchase #6	$227.57	6.499%	$242.3598	$242.36	$242.35	$242.40
Purchase #7	$207.49	5.478%	$218.8563	$218.86	$218.85	$218.90
7 purchase totals =	$1,045.17		$1,131.6366	$1,131.63	$1,131.55	$1,131.80