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	$144.72	7.275%	$155.2484	$155.25	$155.25	$155.20
Purchase #2	$145.80	13.126%	$164.9377	$164.94	$164.95	$164.90
Purchase #3	$85.89	12.238%	$96.4012	$96.40	$96.40	$96.40
Purchase #4	$71.83	11.381%	$80.005	$80.01	$80.00	$80.00
Purchase #5	$99.39	10.231%	$109.5586	$109.56	$109.55	$109.60
Purchase #6	$164.55	5.388%	$173.416	$173.42	$173.40	$173.40
Purchase #7	$126.45	5.698%	$133.6551	$133.66	$133.65	$133.70
7 purchase totals =	$838.63		$913.2220	$913.24	$913.20	$913.20