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	$237.58	11.847%	$265.7261	$265.73	$265.75	$265.70
Purchase #2	$225.59	13.112%	$255.1694	$255.17	$255.15	$255.20
Purchase #3	$95.44	7.511%	$102.6085	$102.61	$102.60	$102.60
Purchase #4	$72.49	10.681%	$80.2327	$80.23	$80.25	$80.20
Purchase #5	$83.67	5.137%	$87.9681	$87.97	$87.95	$88.00
Purchase #6	$231.78	8.625%	$251.771	$251.77	$251.75	$251.80
Purchase #7	$51.82	10.822%	$57.428	$57.43	$57.45	$57.40
7 purchase totals =	$998.37		$1,100.9038	$1,100.91	$1,100.90	$1,100.90