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	$167.75	9.422%	$183.5554	$183.56	$183.55	$183.60
Purchase #2	$79.70	13.516%	$90.4723	$90.47	$90.45	$90.50
Purchase #3	$138.79	9.214%	$151.5781	$151.58	$151.60	$151.60
Purchase #4	$19.88	9.284%	$21.7257	$21.73	$21.75	$21.70
Purchase #5	$148.52	9.588%	$162.7601	$162.76	$162.75	$162.80
Purchase #6	$45.61	13.434%	$51.7372	$51.74	$51.75	$51.70
Purchase #7	$110.63	5.365%	$116.5653	$116.57	$116.55	$116.60
7 purchase totals =	$710.88		$778.3941	$778.41	$778.40	$778.50