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	$213.93	4.455%	$223.4606	$223.46	$223.45	$223.50
Purchase #2	$220.52	13.141%	$249.4985	$249.50	$249.50	$249.50
Purchase #3	$198.76	5.379%	$209.4513	$209.45	$209.45	$209.50
Purchase #4	$143.94	7.496%	$154.7297	$154.73	$154.75	$154.70
Purchase #5	$148.37	9.451%	$162.3924	$162.39	$162.40	$162.40
Purchase #6	$215.69	9.164%	$235.4558	$235.46	$235.45	$235.50
Purchase #7	$107.88	4.296%	$112.5145	$112.51	$112.50	$112.50
7 purchase totals =	$1,249.09		$1,347.5028	$1,347.50	$1,347.50	$1,347.60