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	$127.81	3.388%	$132.1402	$132.14	$132.15	$132.10
Purchase #2	$155.94	13.214%	$176.5459	$176.55	$176.55	$176.50
Purchase #3	$161.37	6.697%	$172.1769	$172.18	$172.20	$172.20
Purchase #4	$127.55	12.210%	$143.1239	$143.12	$143.10	$143.10
Purchase #5	$185.59	4.794%	$194.4872	$194.49	$194.50	$194.50
Purchase #6	$69.75	5.366%	$73.4928	$73.49	$73.50	$73.50
Purchase #7	$73.92	11.725%	$82.5871	$82.59	$82.60	$82.60
7 purchase totals =	$901.93		$974.5540	$974.56	$974.60	$974.50