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	$10.85	3.729%	$11.2546	$11.25	$11.25	$11.30
Purchase #2	$228.84	5.320%	$241.0143	$241.01	$241.00	$241.00
Purchase #3	$143.36	3.788%	$148.7905	$148.79	$148.80	$148.80
Purchase #4	$50.41	6.227%	$53.549	$53.55	$53.55	$53.50
Purchase #5	$53.89	4.198%	$56.1523	$56.15	$56.15	$56.20
Purchase #6	$204.31	10.304%	$225.3621	$225.36	$225.35	$225.40
Purchase #7	$247.74	7.596%	$266.5583	$266.56	$266.55	$266.60
7 purchase totals =	$939.40		$1,002.6811	$1,002.67	$1,002.65	$1,002.80