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	$242.67	7.531%	$260.9455	$260.95	$260.95	$260.90
Purchase #2	$50.81	7.338%	$54.5384	$54.54	$54.55	$54.50
Purchase #3	$140.52	11.619%	$156.847	$156.85	$156.85	$156.80
Purchase #4	$138.40	9.107%	$151.0041	$151.00	$151.00	$151.00
Purchase #5	$79.90	12.109%	$89.5751	$89.58	$89.60	$89.60
Purchase #6	$65.82	12.518%	$74.0593	$74.06	$74.05	$74.10
Purchase #7	$98.96	13.819%	$112.6353	$112.64	$112.65	$112.60
7 purchase totals =	$817.08		$899.6047	$899.62	$899.65	$899.50