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	$112.70	3.327%	$116.4495	$116.45	$116.45	$116.40
Purchase #2	$72.94	7.858%	$78.6716	$78.67	$78.65	$78.70
Purchase #3	$58.61	13.518%	$66.5329	$66.53	$66.55	$66.50
Purchase #4	$113.39	3.804%	$117.7034	$117.70	$117.70	$117.70
Purchase #5	$207.35	7.356%	$222.6027	$222.60	$222.60	$222.60
Purchase #6	$139.46	8.333%	$151.0812	$151.08	$151.10	$151.10
Purchase #7	$245.79	7.425%	$264.0399	$264.04	$264.05	$264.00
7 purchase totals =	$950.24		$1,017.0812	$1,017.07	$1,017.10	$1,017.00