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	$96.90	10.758%	$107.3245	$107.32	$107.30	$107.30
Purchase #2	$245.34	6.836%	$262.1114	$262.11	$262.10	$262.10
Purchase #3	$120.25	11.794%	$134.4323	$134.43	$134.45	$134.40
Purchase #4	$83.79	12.623%	$94.3668	$94.37	$94.35	$94.40
Purchase #5	$214.94	6.197%	$228.2598	$228.26	$228.25	$228.30
Purchase #6	$146.31	10.555%	$161.753	$161.75	$161.75	$161.80
Purchase #7	$107.78	3.818%	$111.895	$111.90	$111.90	$111.90
7 purchase totals =	$1,015.31		$1,100.1428	$1,100.14	$1,100.10	$1,100.20