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	$231.31	12.684%	$260.6494	$260.65	$260.65	$260.60
Purchase #2	$61.90	8.765%	$67.3255	$67.33	$67.35	$67.30
Purchase #3	$63.81	4.387%	$66.6093	$66.61	$66.60	$66.60
Purchase #4	$89.78	11.179%	$99.8165	$99.82	$99.80	$99.80
Purchase #5	$188.95	9.291%	$206.5053	$206.51	$206.50	$206.50
Purchase #6	$9.60	4.713%	$10.0524	$10.05	$10.05	$10.10
Purchase #7	$191.58	4.759%	$200.6973	$200.70	$200.70	$200.70
7 purchase totals =	$836.93		$911.6557	$911.67	$911.65	$911.60