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	$218.40	12.459%	$245.6105	$245.61	$245.60	$245.60
Purchase #2	$250.86	9.164%	$273.8488	$273.85	$273.85	$273.80
Purchase #3	$239.54	9.569%	$262.4616	$262.46	$262.45	$262.50
Purchase #4	$248.37	5.798%	$262.7705	$262.77	$262.75	$262.80
Purchase #5	$107.70	3.438%	$111.4027	$111.40	$111.40	$111.40
Purchase #6	$115.78	4.385%	$120.857	$120.86	$120.85	$120.90
Purchase #7	$98.86	12.225%	$110.9456	$110.95	$110.95	$110.90
7 purchase totals =	$1,279.51		$1,387.8967	$1,387.90	$1,387.85	$1,387.90