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	$62.54	8.631%	$67.9378	$67.94	$67.95	$67.90
Purchase #2	$11.90	10.565%	$13.1572	$13.16	$13.15	$13.20
Purchase #3	$65.67	12.439%	$73.8387	$73.84	$73.85	$73.80
Purchase #4	$216.37	8.693%	$235.179	$235.18	$235.20	$235.20
Purchase #5	$87.60	3.252%	$90.4488	$90.45	$90.45	$90.40
Purchase #6	$36.54	10.290%	$40.3	$40.30	$40.30	$40.30
Purchase #7	$104.31	13.345%	$118.2302	$118.23	$118.25	$118.20
7 purchase totals =	$584.93		$639.0917	$639.10	$639.15	$639.00