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	$110.86	7.799%	$119.506	$119.51	$119.50	$119.50
Purchase #2	$131.98	3.423%	$136.4977	$136.50	$136.50	$136.50
Purchase #3	$163.67	12.857%	$184.7131	$184.71	$184.70	$184.70
Purchase #4	$176.31	11.622%	$196.8007	$196.80	$196.80	$196.80
Purchase #5	$131.27	8.308%	$142.1759	$142.18	$142.20	$142.20
Purchase #6	$31.52	8.766%	$34.283	$34.28	$34.30	$34.30
Purchase #7	$29.98	7.312%	$32.1721	$32.17	$32.15	$32.20
7 purchase totals =	$775.59		$846.1485	$846.15	$846.15	$846.20