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	$155.49	4.461%	$162.4264	$162.43	$162.45	$162.40
Purchase #2	$198.95	3.337%	$205.589	$205.59	$205.60	$205.60
Purchase #3	$99.33	12.222%	$111.4701	$111.47	$111.45	$111.50
Purchase #4	$78.78	7.561%	$84.7366	$84.74	$84.75	$84.70
Purchase #5	$92.46	11.395%	$102.9958	$103.00	$103.00	$103.00
Purchase #6	$166.38	3.868%	$172.8156	$172.82	$172.80	$172.80
Purchase #7	$93.46	10.161%	$102.9565	$102.96	$102.95	$103.00
7 purchase totals =	$884.85		$942.9900	$943.01	$943.00	$943.00