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	$22.48	13.816%	$25.5858	$25.59	$25.60	$25.60
Purchase #2	$66.53	13.718%	$75.6566	$75.66	$75.65	$75.70
Purchase #3	$209.39	7.340%	$224.7592	$224.76	$224.75	$224.80
Purchase #4	$88.38	7.547%	$95.05	$95.05	$95.05	$95.10
Purchase #5	$131.74	12.706%	$148.4789	$148.48	$148.50	$148.50
Purchase #6	$158.86	6.158%	$168.6426	$168.64	$168.65	$168.60
Purchase #7	$244.77	13.658%	$278.2007	$278.20	$278.20	$278.20
7 purchase totals =	$922.15		$1,016.3738	$1,016.38	$1,016.40	$1,016.50