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	$80.61	13.620%	$91.5891	$91.59	$91.60	$91.60
Purchase #2	$244.81	4.732%	$256.3944	$256.39	$256.40	$256.40
Purchase #3	$72.80	5.576%	$76.8593	$76.86	$76.85	$76.90
Purchase #4	$64.58	9.160%	$70.4955	$70.50	$70.50	$70.50
Purchase #5	$71.58	9.676%	$78.5061	$78.51	$78.50	$78.50
Purchase #6	$207.58	13.505%	$235.6137	$235.61	$235.60	$235.60
Purchase #7	$126.45	4.453%	$132.0808	$132.08	$132.10	$132.10
7 purchase totals =	$868.41		$941.5389	$941.54	$941.55	$941.60