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	$115.93	3.236%	$119.6815	$119.68	$119.70	$119.70
Purchase #2	$78.26	6.162%	$83.0824	$83.08	$83.10	$83.10
Purchase #3	$17.25	9.744%	$18.9308	$18.93	$18.95	$18.90
Purchase #4	$42.39	4.786%	$44.4188	$44.42	$44.40	$44.40
Purchase #5	$103.64	5.596%	$109.4397	$109.44	$109.45	$109.40
Purchase #6	$62.94	4.629%	$65.8535	$65.85	$65.85	$65.90
Purchase #7	$41.83	12.314%	$46.9809	$46.98	$47.00	$47.00
7 purchase totals =	$462.24		$488.3876	$488.38	$488.45	$488.40