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	$149.27	13.627%	$169.611	$169.61	$169.60	$169.60
Purchase #2	$237.91	10.367%	$262.5741	$262.57	$262.55	$262.60
Purchase #3	$66.96	6.715%	$71.4564	$71.46	$71.45	$71.50
Purchase #4	$191.91	7.128%	$205.5893	$205.59	$205.60	$205.60
Purchase #5	$36.71	5.780%	$38.8318	$38.83	$38.85	$38.80
Purchase #6	$109.96	13.179%	$124.4516	$124.45	$124.45	$124.50
Purchase #7	$142.57	13.335%	$161.5817	$161.58	$161.60	$161.60
7 purchase totals =	$935.29		$1,034.0959	$1,034.09	$1,034.10	$1,034.20