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	$127.30	11.659%	$142.1419	$142.14	$142.15	$142.10
Purchase #2	$182.70	7.658%	$196.6912	$196.69	$196.70	$196.70
Purchase #3	$164.93	3.579%	$170.8328	$170.83	$170.85	$170.80
Purchase #4	$249.76	13.266%	$282.8932	$282.89	$282.90	$282.90
Purchase #5	$241.57	13.387%	$273.909	$273.91	$273.90	$273.90
Purchase #6	$154.46	12.158%	$173.2392	$173.24	$173.25	$173.20
Purchase #7	$185.35	10.302%	$204.4448	$204.44	$204.45	$204.40
7 purchase totals =	$1,306.07		$1,444.1521	$1,444.14	$1,444.20	$1,444.00