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	$99.74	13.231%	$112.9366	$112.94	$112.95	$112.90
Purchase #2	$17.27	7.167%	$18.5077	$18.51	$18.50	$18.50
Purchase #3	$168.67	3.626%	$174.786	$174.79	$174.80	$174.80
Purchase #4	$70.92	4.442%	$74.0703	$74.07	$74.05	$74.10
Purchase #5	$201.30	10.600%	$222.6378	$222.64	$222.65	$222.60
Purchase #6	$25.52	8.161%	$27.6027	$27.60	$27.60	$27.60
Purchase #7	$190.80	13.184%	$215.9551	$215.96	$215.95	$216.00
7 purchase totals =	$774.22		$846.4962	$846.51	$846.50	$846.50