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	$224.52	7.562%	$241.4982	$241.50	$241.50	$241.50
Purchase #2	$111.39	8.194%	$120.5173	$120.52	$120.50	$120.50
Purchase #3	$128.52	3.278%	$132.7329	$132.73	$132.75	$132.70
Purchase #4	$62.36	6.816%	$66.6105	$66.61	$66.60	$66.60
Purchase #5	$231.64	12.157%	$259.8005	$259.80	$259.80	$259.80
Purchase #6	$164.66	9.237%	$179.8696	$179.87	$179.85	$179.90
Purchase #7	$34.45	9.400%	$37.6883	$37.69	$37.70	$37.70
7 purchase totals =	$957.54		$1,038.7173	$1,038.72	$1,038.70	$1,038.70