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	$151.97	9.615%	$166.5819	$166.58	$166.60	$166.60
Purchase #2	$214.58	13.528%	$243.6084	$243.61	$243.60	$243.60
Purchase #3	$94.61	3.452%	$97.8759	$97.88	$97.90	$97.90
Purchase #4	$171.99	7.386%	$184.6932	$184.69	$184.70	$184.70
Purchase #5	$221.96	6.271%	$235.8791	$235.88	$235.90	$235.90
Purchase #6	$69.67	13.185%	$78.856	$78.86	$78.85	$78.90
Purchase #7	$105.99	4.812%	$111.0902	$111.09	$111.10	$111.10
7 purchase totals =	$1,030.77		$1,118.5847	$1,118.59	$1,118.65	$1,118.70