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	$57.59	8.847%	$62.685	$62.69	$62.70	$62.70
Purchase #2	$228.80	9.266%	$250.0006	$250.00	$250.00	$250.00
Purchase #3	$134.28	4.546%	$140.3844	$140.38	$140.40	$140.40
Purchase #4	$87.72	3.566%	$90.8481	$90.85	$90.85	$90.80
Purchase #5	$226.55	4.149%	$235.9496	$235.95	$235.95	$235.90
Purchase #6	$109.91	9.726%	$120.5998	$120.60	$120.60	$120.60
Purchase #7	$109.94	7.421%	$118.0986	$118.10	$118.10	$118.10
7 purchase totals =	$954.79		$1,018.5661	$1,018.57	$1,018.60	$1,018.50