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	$213.43	10.684%	$236.2329	$236.23	$236.25	$236.20
Purchase #2	$114.69	10.787%	$127.0616	$127.06	$127.05	$127.10
Purchase #3	$182.42	9.821%	$200.3355	$200.34	$200.35	$200.30
Purchase #4	$201.30	9.255%	$219.9303	$219.93	$219.95	$219.90
Purchase #5	$181.50	13.792%	$206.5325	$206.53	$206.55	$206.50
Purchase #6	$72.45	10.548%	$80.092	$80.09	$80.10	$80.10
Purchase #7	$14.55	4.704%	$15.2344	$15.23	$15.25	$15.20
7 purchase totals =	$980.34		$1,085.4192	$1,085.41	$1,085.50	$1,085.30