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	$180.29	11.429%	$200.8953	$200.90	$200.90	$200.90
Purchase #2	$106.90	9.132%	$116.6621	$116.66	$116.65	$116.70
Purchase #3	$162.62	13.523%	$184.6111	$184.61	$184.60	$184.60
Purchase #4	$59.33	5.389%	$62.5273	$62.53	$62.55	$62.50
Purchase #5	$130.26	13.401%	$147.7161	$147.72	$147.70	$147.70
Purchase #6	$35.45	10.784%	$39.2729	$39.27	$39.25	$39.30
Purchase #7	$118.86	11.224%	$132.2008	$132.20	$132.20	$132.20
7 purchase totals =	$793.71		$883.8856	$883.89	$883.85	$883.90