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	$52.84	4.293%	$55.1084	$55.11	$55.10	$55.10
Purchase #2	$172.88	7.344%	$185.5763	$185.58	$185.60	$185.60
Purchase #3	$123.25	4.615%	$128.938	$128.94	$128.95	$128.90
Purchase #4	$104.72	13.133%	$118.4729	$118.47	$118.45	$118.50
Purchase #5	$219.72	8.362%	$238.093	$238.09	$238.10	$238.10
Purchase #6	$247.31	5.395%	$260.6524	$260.65	$260.65	$260.70
Purchase #7	$127.83	3.636%	$132.4779	$132.48	$132.50	$132.50
7 purchase totals =	$1,048.55		$1,119.3189	$1,119.32	$1,119.35	$1,119.40