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	$192.34	12.779%	$216.9191	$216.92	$216.90	$216.90
Purchase #2	$85.26	3.574%	$88.3072	$88.31	$88.30	$88.30
Purchase #3	$9.77	4.673%	$10.2266	$10.23	$10.25	$10.20
Purchase #4	$101.95	3.592%	$105.612	$105.61	$105.60	$105.60
Purchase #5	$64.86	11.779%	$72.4999	$72.50	$72.50	$72.50
Purchase #6	$121.59	10.529%	$134.3922	$134.39	$134.40	$134.40
Purchase #7	$107.45	12.338%	$120.7072	$120.71	$120.70	$120.70
7 purchase totals =	$683.22		$748.6642	$748.67	$748.65	$748.60