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	$95.31	7.774%	$102.7194	$102.72	$102.70	$102.70
Purchase #2	$167.46	3.685%	$173.6309	$173.63	$173.65	$173.60
Purchase #3	$100.90	11.335%	$112.337	$112.34	$112.35	$112.30
Purchase #4	$113.65	3.868%	$118.046	$118.05	$118.05	$118.00
Purchase #5	$173.67	13.334%	$196.8272	$196.83	$196.85	$196.80
Purchase #6	$250.28	5.291%	$263.5223	$263.52	$263.50	$263.50
Purchase #7	$173.49	10.579%	$191.8435	$191.84	$191.85	$191.80
7 purchase totals =	$1,074.76		$1,158.9263	$1,158.93	$1,158.95	$1,158.70