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	$114.27	12.458%	$128.5058	$128.51	$128.50	$128.50
Purchase #2	$184.41	13.382%	$209.0877	$209.09	$209.10	$209.10
Purchase #3	$224.48	3.259%	$231.7958	$231.80	$231.80	$231.80
Purchase #4	$75.78	5.434%	$79.8979	$79.90	$79.90	$79.90
Purchase #5	$167.42	4.357%	$174.7145	$174.71	$174.70	$174.70
Purchase #6	$160.40	13.188%	$181.5536	$181.55	$181.55	$181.60
Purchase #7	$65.91	9.796%	$72.3665	$72.37	$72.35	$72.40
7 purchase totals =	$992.67		$1,077.9218	$1,077.93	$1,077.90	$1,078.00