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	$237.77	11.579%	$265.3014	$265.30	$265.30	$265.30
Purchase #2	$103.33	10.720%	$114.407	$114.41	$114.40	$114.40
Purchase #3	$180.42	7.175%	$193.3651	$193.37	$193.35	$193.40
Purchase #4	$102.69	9.205%	$112.1426	$112.14	$112.15	$112.10
Purchase #5	$61.67	8.531%	$66.9311	$66.93	$66.95	$66.90
Purchase #6	$104.86	11.208%	$116.6127	$116.61	$116.60	$116.60
Purchase #7	$88.71	13.412%	$100.6078	$100.61	$100.60	$100.60
7 purchase totals =	$879.45		$969.3677	$969.37	$969.35	$969.30