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	$47.47	10.614%	$52.5085	$52.51	$52.50	$52.50
Purchase #2	$250.75	6.240%	$266.3968	$266.40	$266.40	$266.40
Purchase #3	$123.68	4.185%	$128.856	$128.86	$128.85	$128.90
Purchase #4	$132.50	3.117%	$136.63	$136.63	$136.65	$136.60
Purchase #5	$53.51	6.335%	$56.8999	$56.90	$56.90	$56.90
Purchase #6	$153.80	4.362%	$160.5088	$160.51	$160.50	$160.50
Purchase #7	$193.37	10.576%	$213.8208	$213.82	$213.80	$213.80
7 purchase totals =	$955.08		$1,015.6208	$1,015.63	$1,015.60	$1,015.60