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	$159.31	7.181%	$170.7501	$170.75	$170.75	$170.80
Purchase #2	$119.31	11.121%	$132.5785	$132.58	$132.60	$132.60
Purchase #3	$148.89	7.162%	$159.5535	$159.55	$159.55	$159.60
Purchase #4	$159.55	9.402%	$174.5509	$174.55	$174.55	$174.60
Purchase #5	$216.55	5.133%	$227.6655	$227.67	$227.65	$227.70
Purchase #6	$11.30	3.640%	$11.7113	$11.71	$11.70	$11.70
Purchase #7	$166.65	10.710%	$184.4982	$184.50	$184.50	$184.50
7 purchase totals =	$981.56		$1,061.3080	$1,061.31	$1,061.30	$1,061.50