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	$230.95	3.316%	$238.6083	$238.61	$238.60	$238.60
Purchase #2	$15.34	5.650%	$16.2067	$16.21	$16.20	$16.20
Purchase #3	$16.61	9.119%	$18.1247	$18.12	$18.10	$18.10
Purchase #4	$69.30	13.675%	$78.7768	$78.78	$78.80	$78.80
Purchase #5	$224.99	7.486%	$241.8328	$241.83	$241.85	$241.80
Purchase #6	$235.38	12.718%	$265.3156	$265.32	$265.30	$265.30
Purchase #7	$177.60	4.342%	$185.3114	$185.31	$185.30	$185.30
7 purchase totals =	$970.17		$1,044.1763	$1,044.18	$1,044.15	$1,044.10