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	$224.79	13.492%	$255.1187	$255.12	$255.10	$255.10
Purchase #2	$146.28	7.193%	$156.8019	$156.80	$156.80	$156.80
Purchase #3	$106.98	11.214%	$118.9767	$118.98	$119.00	$119.00
Purchase #4	$98.42	8.872%	$107.1518	$107.15	$107.15	$107.20
Purchase #5	$111.84	6.467%	$119.0727	$119.07	$119.05	$119.10
Purchase #6	$103.61	7.487%	$111.3673	$111.37	$111.35	$111.40
Purchase #7	$168.33	13.554%	$191.1454	$191.15	$191.15	$191.10
7 purchase totals =	$960.25		$1,059.6345	$1,059.64	$1,059.60	$1,059.70